Open access peer-reviewed chapter

Biomarkers in Breast Cancer

Written By

Serena Bertozzi, Ambrogio P Londero, Luca Seriau, Roberta Di Vora, Carla Cedolini and Laura Mariuzzi

Submitted: 15 October 2017 Reviewed: 18 April 2018 Published: 05 November 2018

DOI: 10.5772/intechopen.77320

From the Edited Volume

Biomarker - Indicator of Abnormal Physiological Process

Edited by Ghousia Begum

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Breast cancer is the most common cancer in women and its incidence experienced an important increase, thanks to the introduction of a systematic screening. The increased incidence of early breast cancer has led to debates on its over-treatment, which may cause unnecessary harm to patients with favorable prognosis. Therefore, modern research is in the quest of finding the perfect prognostic marker to avoid overtreatment in patients with a favorable prognosis. In this perspective, many molecular markers have been studied in the last decades in order to provide both a useful prognostic tool, able to determine whether the cancer is likely to be indolent or aggressive, and a possible therapeutic target. In this chapter, we review the current knowledge about the principal biomarkers, which are usually immunohistochemically tested on breast surgical specimens, including ER and PR, Mib1/Ki-67 and HER2/neu expression. Furthermore, we will analyze other possible prognostic markers which may have in the future a key role in breast cancer management, such as several multigene panels (OncotypeDX, Mammaprint, NanoString Prosigma). Finally, we will discuss the role of genetic tests for some know genetic mutations associated with higher breast cancer susceptibility (BRCA1 and 2 genes).


  • breast cancer
  • biomolecular markers
  • biohumoral markers
  • therapy target
  • prognostic factors

1. Introduction

Breast cancer is the most common cancer in women, accounting for about one-third of cancer cases in women and more than 10% of all cancers worldwide [1], and its incidence experienced an important increase, thanks to the introduction at the beginning of this century of a systematic mammographic screening in the most developed countries, and the subsequent successful detection of an always greater number of early breast cancers [2, 3, 4]. The incidence of breast cancer is also rapidly rising in developing countries, so that it will become in the next decades a major health burden in both developed and developing countries.

Improvement in the adjuvant chemotherapy and endocrine therapy decreased breast cancer mortality by approximately 50%. However, the increased incidence of early breast cancer has led to debates on its overtreatment, which not only increases social and family burden, but may also cause unnecessary harm to patients with a favorable prognosis [5, 6]. Therefore, the research is focusing on the development of new adjuvant therapies with a more precise target and fewer side effects. In this perspective, many molecular markers have been studied in the last decades in order to provide both a useful prognostic tool, able to determine whether the cancer is likely to be indolent or aggressive [7, 8], and a possible therapeutic target.

Breast cancer includes a heterogeneous group of tumors with a wide spectrum of morphologically and molecularly different subtypes, resulting in different biological behaviors, presentation, and prognosis. Along with the disease stage and the patient performance, the molecular pattern of the tumor is fundamental to identify patients who will particularly benefit from a given treatment. Among the molecular markers associated with breast cancer, the estrogen receptor (ER), the progesterone receptor (PR), the human epidermal growth factor receptor (HER2) and the Mib1/Ki-67 proliferation index are the most important ones and are firmly established in the standard care of all primary, recurrent, and metastatic breast cancer patients.

In this chapter, we review the clinical relevance of the principal biomarkers, which are usually immunohistochemically tested on breast surgical specimens. We discuss about their implication in the prognosis and treatment of breast cancer patients, and thus how this information is translated to treatment decision-making, the valid assays for these markers, and the guidelines for testing them. Furthermore, we analyze other possible prognostic markers which may have in the future a key role in breast cancer management, such as several multigene panels, which have been developed to predict the possibility of distant metastasis in the hormonal receptor-positive disease [9, 10, 11]. Finally, we discuss the role of genetic tests for some know genetic mutations associated with higher breast cancer susceptibility in the screening and follow-up of women at high risk.


2. Estrogen and progesterone receptor: Prognosis prediction and treatment planning

Human breast cancer usually depends on sexual hormones for its growth, as it arises from breast tissue that normally responds to endogenous hormones [12]. As in 1896 was firstly noticed that bilteral oophorectomy could induce a significant regression in breast cancer in the fertile age [13], endocrine therapy became quickly a standard of care in the treatment of breast cancer, but only one-third of patients responded.

Then, as in the early 1960s, radiolabeled estrogens were observed to concentrate on specific target organs, the existence of an estrogen receptor (ER) was hypothesized, which could be a predictive factor for the endocrine responsiveness of breast cancer to ovarian ablation [14, 15]. In fact, about 60% of ER-positive tumors, but only about 8% of ER-negative ones showed an objective response to endocrine therapy. The small proportion of patients who respond to hormone therapy with ER-negative disease may be mostly due to false-negative receptor assay results.

The identification of the estrogen receptor has not only proved to be a successful therapeutic target for the treatment and prevention of breast cancer, but has also represented a selective molecular model for all subsequent efforts to design oncological targeted therapies. Estrogen and progesterone receptor (PR), together with the HER2 status represent the most important molecular markers in the standard care of all primary, recurrent, and metastatic breast cancer patients, and the standardized assessment of the ER/PR/HER2 status is crucial in the evaluation of every newly diagnosed breast cancer.

Hormonal receptor-positive disease represents usually an indolent and slowly growing tumor with longer time to recurrence. The responsiveness of a tumor to hormone therapy is an important parameter in breast cancer management in both adjuvant and metastatic settings. The clinical aspects of anti-hormonal treatments are exposed in the following sections.

2.1. Biology of hormone receptors

The ER is a ligand-regulated, cytoplasmic receptor that belongs to the steroid nuclear receptor family, which in the ER-positive breast disease, promotes cell proliferation, survival, and invasion. The key components of ER are the DNA-binding domain, which binds with high affinity and specificity to estrogen response elements (ERE sequence) of DNA to regulate the transcription rates of target genes, and the ligand-binding domain, which binds estrogens [16]. The binding of estrogen to its receptor is essential for its translocation into the nucleus, where it functions as a transcription factor and transduces hormonal signals into a large variety of physiological responses in various target organs.

Two forms of ER, ERα and ERβ, are encoded by two separate genes that are differentially expressed in tissues. In the normal mammary gland, both ERα and ERβ bind estradiol to control cell proliferation and differentiation [17, 18]. ERα is also responsible for estrogen-induced mitogenic signaling in epithelial cells in breast, uterine, and ovarian tissues [19] and is prevalently expressed by breast cancer cells [20], whereas ERβ is usually associated with less aggressive tumors, as it inhibits both ERα-mediated transcription and estradiol-induced proliferation in various types of cancer cells [21]. The ERα/ERβ ratio may play a critical role in the regulation of estradiol activity in breast cancer cells [22].

Estradiol binding to ER activates the receptor through phosphorylation, which undergoes conformational changes and dissociates proteins which usually tightly wrap the DNA [23]. Thereafter, ER binds to the ERE sequence within the gene promoter, and dynamically and sequentially recruits various regulatory protein complexes that contribute to chromatin remodeling and enhance transcriptional activity [24].

ER-mediated transcription involves also other multiple coregulatory proteins, which coordinately act to influence gene transcription, cell cycle regulation, cell differentiation and apoptosis. Nuclear receptors coactivators of ER include the ubiquitary general transcription factor P300/CBP, some methyltransferases such as CARM1 and PRMT1, some members of the p160 protein family such as the steroid receptor coactivators (SRC1, SRC2, and SRC3) [25, 26].

The regulation of ER and PR function can occur at three levels: differential translation of exons, splicing of their mRNA, and post-translational modifications. These lasts include phosphorylation, ubiquitylation, acetylation, and methylation. Among the multiple kinases that can phosphorylate ERα are p38 mitogen-activated protein kinase (MAPK), cyclin A-CDK2, CDK7, c-Src, pp90rsk1, extracellular regulated kinase (Erk) 1 and 2, protein kinase A (PKA) and B (Akt) [27, 28, 29, 30, 31, 32, 33, 34, 35]. The effects of this phosphorylation involve receptor turnover, cellular localization, and transcriptional activity and are complex and interdependent. The PR can be phosphorylated at different sites coordinately regulated by ligands or kinases [36].

Few mutations of the ERα gene have been reported in the literature, resulting in a receptor with hypersensitivity to the estrogen-mediated growth-promoting effects. These mutations in breast cancer correlate with older age, larger tumor size, nodal involvement, and poor prognosis [37, 38, 39].

Along with their classical genomic activity, ER and PR exhibit also a more rapid, nongenomic activity, which occurs within seconds to minutes independently of gene transcription, by mediating signaling cascades originating from the membrane or the cytoplasm through direct interaction with signal-transduction mediators [40, 41]. ER may establish a cross talk with other signal transduction pathways, such as that of growth factors, using its membrane and cytoplasmic receptors to transmit their signals through kinase cascades, triggering the phosphorylation and activation of the epidermal growth factor receptors (EGFR), insulin-like growth factor-1R (IGF-1R), transforming growth factor TGFα, Src kinase, Shc adaptor protein, and phosphatidylinositol 3-kinase (PI3K), and the inhibition of TGFβ and tyrosine phosphatases [20, 42, 43, 44, 45]. Finally, ER may also use calcium, cyclic adenosine monophosphate (cAMP), and other second messengers for signal transduction.

2.2. Clinical relevance of hormone receptors

Hormone receptors are expressed by about two-thirds of invasive breast cancers in women younger than 50 and approximately 80% of tumors in women older than 50 [46]. Measurement of hormone receptors has become a routine part of the evaluation of breast cancers, as they represent a predictive factor for hormone therapy responsiveness. Both ER and PR increasing levels directly correlate with better response, longer time to treatment failure, and longer survival [47, 48].

Hormone receptor expression represents also an important favorable prognostic factor, being an important marker of growth rate, rather than metastatic potential. In particular, patients with ER+/PR+ tumors have a better prognosis than patients with ER+/PR- tumors, who in turn have a better prognosis than patients with ER-/PR- tumors [49]. ER expression is significantly associated with some favorable prognostic indicators, such as older age, low grading, lower fraction of dividing cells, lower genetic mutation, but not with nodal involvement [46, 50, 51, 52, 53].

Adjuvant hormone therapy can halve the recurrence rate of patients with ER-positive breast cancer [54] and, due to its quite limited side effects, it can be administered with success also in the elderly or in the presence of comorbidities, and responses can last for many years in some patients with metastatic disease. Patients with stage I ER-positive breast cancer, who receive no systemic therapy, have a 5–10% lower probability of recurrence at 5 years in comparison with ER-negative patients [55]. On the other hand, in ER-negative tumors are unlikely to respond to hormone therapy and respond better to cytotoxic chemotherapy.

The literature demonstrates that the benefit of 5 years of adjuvant tamoxifen treatment depends on the tumor ER and PR status [54, 56], and the efficacy of tamoxifen in reducing local, contralateral and distant relapse or death was strongly confirmed by more recent large prospective trials [57, 58]. A marginally significant relationship between ER level and time to recurrence was observed also in patients treated with aromatase inhibitors [59]. However, studies about adjuvant tamoxifen in early breast cancers did not show any benefit of PR expression among ER-positive patients, but only a benefit among ER-negative patients [54, 60, 61]. Definitely, ER+/PR+ tumors had a 15–30% lower risk of recurrence and death than ER+/PR- ones [49].

Hormone therapy may be an interesting option also in the advanced disease, as the level of ER expression is associated with good responses in the ER-positive disease, and provides good palliation, better quality of life, and improved survival [62]. In fact, approximately 30–40% of patients with ER-positive metastatic disease will respond to first-line hormone therapies, another 20% will experience disease stabilization, and despite a gradual efficacy decline, about 20–30% will respond to subsequent lines of hormone therapy [63]. ER status is also prognostic for the site of metastasis, metastasizing ER-positive tumors more frequently to the bone, soft tissue, or the reproductive and genital tracts, and ER-negative ones to visceral organs or the brain [64].

As the hormone receptor status of the metastases should be more predictive than that of the primary tumor, before making treatment decisions, the molecular markers of breast cancer should be retested in the metastatic lesions when possible, due to the risk of discordance between the hormone receptor status between the relapse/metastases and the primary tumor. In fact, a conversion rate of 20–30% has been reported from ER-positive to ER-negative status, related with a poorer prognosis, while less frequent conversion has been reported from ER-negative to ER-positive status [65, 66, 67, 68]. The same happens for what concerns PR expression in metastatic lesions, which often converts from PR-positive to PR-negative [66, 67].

Beyond the probable technical causes of false-negative or false-positive results, possible explanations for the hormone status changes include the tumor dedifferentiation over time and the intratumoral heterogeneity, leading to clonal selection of hormone receptor negative and more resistant clones, as an adaptive mechanism to prior treatments [68]. Apart from the hormon status change, the resistance to endocrine therapy may be explained by the modulation of many cellular signaling networks, which usually provide alternative mitogenic and survival stimuli for the cells. Therefore, multigene predictive scores have been developed to predict tumors hormonal responsiveness, such as the Oncotype DX 21 gene assay, which includes several downstream ER-regulated genes and several proliferation genes in addition to ER mRNA, and will be discussed in another section [11].

The results of adjuvant chemotherapy trials support that ER-negative tumors derive more benefit from chemotherapy than ER-positive ones, as well as luminal A (ER/PR+/HER2-) tumors [54, 69]. A study comparing adjuvant TAC (docetaxel-adriamycin-cyclophosphamide) with FAC (fluorouracil-adriamycin-cyclophosphamide) showed a benefit of adding taxanes regardless of ER status, as they exhibit endocrine effects by inducing amenorrhea in premenopausal women [70]. On the other hand, as expected, the ovarian ablative effects of chemotherapy are not observed in postmenopausal patients. Neoadjuvant chemotherapy trials have also shown the effect of ER status in pathologic complete response (pCR) rates, which result significantly higher in the ER-positive group than in ER-negative one [71].

2.3. Methods for measuring hormone receptors

Various assay methods have been used to measure ER expression in breast cancer specimens, which is fundamental for the therapeutic planning. The dextran-coated charcoal/ligand-binding assay (DCC/LBA) was the first available standard inked immunosorbent assay (ELISA). Thereafter, since 1990s, immunohistochemistry (IHC) of formalin-fixed paraffin-embedded specimens began to replace the DCC assay because it needs smaller tissue amounts, does not require fresh/frozen tissue, correlates staining with histology, and allows the storage and retrieval of archived slides for later testing [72].

The last guidelines for hormone receptor testing, reported by the Society of Clinical Oncology (ASCO)/Collage of American Pathologists (CAP) in 2010, establish mandatory proficiency testing and inspection criteria to improve the accuracy of these tests [73]. Breast resection specimens should be fixed as quickly as possible (within 1 h from reesection) in an adequate volume of fixative (optimally 10-fold greater than the volume of the specimen). After being received in the pathology laboratory, specimens should be oriented and carefully inked for surgical margin assessment, sectioned at 5 mm intervals, and placed in 10% neutral (phosphate) buffered formalin for no less than 6 h and for not more than 72 h before processing.

After treatment for antigen retrieval, the tissue sections are incubated with a primary antibody directed against the ER or PR, and subsequently with a secondary detection systems that are conjugated to an enzyme to amplify the chromogenic signal, and finally microscopically evaluated. External and internal controls can be used to ensure the proper performance of IHC test. The percentage of cells with nuclear staining is reported by either estimation or quantitation, which may be performed either manually or by image analysis. Both the average intensity (weak, moderate, strong) and extent of staining (as a percentage) are reported. ER or PR expression is considered positive or negative in case of immunoreaction in respectively ≥1 or <1% of tumor cell nuclei [73].


3. HER2/neu testing: Prognosis prediction and targeted therapies

3.1. Biology of HER2/neu

The human epidermal growth factor receptor 2 (HER2/neu) gene, localized on chromosome 17, encodes a a 185 kDa, transmembrane member of the tyrosine kinase epidermal growth factor receptors, which are normally expressed at low levels in all epithelial cells in normal fetal and adult tissues, but are also essential for cancer proliferation and survival [74]. HER2 gene amplification has been associated with increased levels of expression of HER2 mRNA and protein product, which lead to oncogenic signaling and resultant self-sufficiency in growth signals, uncontrolled proliferation, sustained angiogenesis, survival, enhanced invasion, and metastasis processes, which are drivers of carcinogenesis [75, 76, 77]. The HER2/neu gene results amplified in a variable percentage of breast [77, 78], ovarian [77], bladder, endometrial [79], salivary gland [80], and gastric cancer [81].

The human epidermal growth factor receptor (HER) family consists of four members: EGFR/ErbB1, HER2/ErbB2, HER3/ErbB3, and HER4/ErbB4. The structure of these receptors consists of a ligand-binding extracellular domain, a transmembrane domain, and a cytoplasmic catalytic kinase domain that drives downstream signaling pathways, such as the PI3K/Akt/mTOR and RAS/RAF/MEK/ERK ones [82]. HER heterodimers are more potent in signal transduction than are homodimers. HER2 is the preferred partner for dimerization, triggering with its overexpression breast cancer progression with a poor prognosis, and the HER2-HER3 heterodimer is known to be the most potent oncogenic combination in breast cancer.

HER2 overexpression ultimately activates ligand-independent HER2/HER3/PI3K complex formation and kinase activity in tumor cells, so that the resistance to trastuzumab can be circumvented through PI3K inhibition, as well as gain-of-function mutations of PI3K and the loss of PTEN. Furthermore, the upregulation of insulin-like growth factor receptor 1 (IGF-1R) results in sustained activation of the PI3K/Akt pathway, thereby leading to resistance to anti-hormonal and HER2-targeted therapies.

3.2. Clinical relevance of HER2/neu

Having a look at the currrent literature, HER2 results amplified in approximately 15–30% of breast cancers [75, 83]. HER2 overexpression, in the absence of adjuvant treatment, correlates with a poor prognosis in terms of both overall and disease-free survival, independent of tumor size, grade and hormone receptor status [84]. However, HER2 is also an important predictive marker for responsiveness to HER2-targeted therapies, in both metastatic and adjuvant settings [85, 86].

Trastuzumab, the most famous humanized monoclonal antibody against HER2, significantly improves response rates, time to progression and survival when used alone or added to chemotherapy in both early stage and metastatic breast cancer [87]. Other HER2-targeted drugs, including the tyrosine kinase inhibitor lapatinib, the antibody pertuzumab, and the antibody drug conjugate adotrastuzumab emtansine (T-DM1), improve outcomes in HER2-positive metastatic breast cancer [88, 89, 90].

A controversial association exists between HER2 positivity and resistance to hormone therapies, but randomized trials in either adjuvant or metastatic settings failed to provide supporting evidence. [91]. This probably happens due to a physiological cross talk between the HER2 and ER signal transduction pathways, but other mechanisms of hormone independent endocrine resistance of HER2-expressing cells have been described, such as phosphorylation of the ER, ligand-independent ER activation, and regulation of hormone receptor expression [92]. Moreover, some data suggest that endocrine resistance may be specific to selective estrogen modulator (SERM) therapy such as tamoxifen and perhaps not to estrogen depletion therapies such as aromatase inhibitors [59, 93]. Furthermore, the response to ligand-depleting therapies such as ovarian ablation or aromatase inhibitors is not affected by HER2 overexpression.

HER2 may be associated with either sensitivity or resistance to some chemotherapeutic agents. For example, HER2 positivity is associated with better outcomes in response to adjuvant anthracycline containing regimens in most studies, probably due to the coamplification of HER2 with topoisomerase II, which is the direct target of anthracyclines [94]. Anyway, the combination of trastuzumab and anthracycline has cardiotoxicity concerns, so that an accurate determination of HER2 alterations in breast carcinomas is mandatory. On the other hand, data about the possibile correlation of HER2 positivity with responsiveness to paclitaxel containing chemotherapy are still contradictory [95].

3.3. Methods for measuring HER2/neu

HER2 gene amplification is directly correlated with its mRNA expression and protein levels, and HER2 status can potentially be evaluated at any of these levels. A great number of commercially available testing kits are approved from FDA for the assessment of patients suitable for the treatment whit trastuzumab (humanized mouse 4D5 monoclonal antibody) may be a suitable treatment. Overexpression of the HER2 protein product may be evaluated by Western blotting, ELISA or IHC; overexpression of its mRNA by Northern blotting or RT-PCR, and its gene amplification by fluorescence (FISH), chromogenic (CISH) or silver-enhanced in situ hybridization (SISH) [96].

FISH is more accurate, reproducible, and robust than IHC [97], but IHC has been more widely used as the primary test for HER2 status because it results quicker, is viewed using a conventional bright-field microscope, permits parallel viewing of tumor morphological features, and stained tissues do not degrade over time [98]. Moreover, automated IHC techniques may enable more rapid testing.

Recommendations for tissue handling as well as preanalytic, analytic, and postanalytic factors in ER/PR testing are also suitable for HER2 testing. Laboratories performing these tests should follow all accreditation requirements, which conform to the 2010 ASCO/CAP recommendations for ER/PR testing, one of which is the initial testing validation [83]. Laboratories are responsible for ensuring the reliability and accuracy of their testing results and should review and document external and internal controls with each test and each batch of tests.

The final IHC result is classified as 3+ in the case of a complete circumferential membrane staining in >10% of neoplastic cells, 2+ in the presence of moderate circumferential membrane staining of >10% of neoplastic cells, 1+ or 0 if there is incomplete membrane staining or no staining in >10% of neoplastic cells. A positive result includes the 3+ and the 2+ in the presence of a ISH confirmation [83].


4. Mib1/Ki-67: Prognosis prediction and treatment planning

Numerous measures of tumor cell proliferation have been studied over time, including thymidine labeling index, flow cytometry and S-phase fraction, thymidine kinase, cyclins D and E and their inhibitors p27 and p21, topoisomerase IIα, p53, bax, bcl-2, and Ki67, but methodological shortcomings precluded attribution of prognostic or predictive significance to any of these potential markers [99].

The mitotic index, which is one of the three components of the tumor grading assessment, results the strongest prognostic discriminant in node-negative breast cancer, being the most significant predictor of survival, and rendering less significant the other two elements of tumor grading evaluation, pleomorphism and tubular formation [100]. In particular, patients with mitotic index ≥10 should be considered at high risk and be offered adjuvant therapy.

Mib1/Ki-67 is a proliferation index used as both a prognostic and predictive marker, although its widespread use is limited by the lack of standardization of the assay and its interpretation [99, 101]. This marker of proliferation results an independent prognostic factor for DFS, is significantly predictive for responsiveness to both adjuvant chemotherapy and endocrine therapy, and is predictive for pathological complete response in the neoadjuvant setting [102, 103]. In fact, the Mib1/Ki-67 decrease in the post-treatment samples of women who underwent neoadjuvant therapies is a strong independent predictor of better clinical outcomes [104].


5. Genomic markers, prognosis, and personalized treatment

In the past, breast cancers were simply treated based on some clinicopathological features, such as tumor size, lymph node status, patients age and menopausal status, and tumor biomarkers such as ER, PR, and HER2/neu. Then, systemic chemotherapy was applied nearly universally to locally advanced breast cancers regardless of their biomolecular profile, and to about 60% of early breast cancers, but often without any significant effect on women prognosis [105]. As a consequence, a great debate has emerged about quality-of-life issues, acute and long-term side effects of systemic therapies, and the cost of unnecessary treatments [54, 106]. Therefore, in the last decades, quantitative approaches for prognosis prediction and treatment individualization have been developed, and genomic and molecular technologies are routinely applied to prevent overtreatments.

Recently, thanks to the increased level of knowledge regarding the molecular pathways and underlying genetic changes in breast cancer, the molecular signatures of gene expression have been correlated with breast cancer recurrence risk [7, 107, 108]. Anyway, their current clinical application is still limited due to reproducibility questions and the need for fresh or frozen tissue.

In this section, we discuss about susceptibility genes, the carriers of which results to have an increased breast cancer risk and consequently deserve a more frequent and specific screening, and about some signatures, which are usually used to predict breast cancer responsiveness to adjuvant and neoadjuvant therapies.

5.1. BRCA1 and BRCA2

Inherited susceptibility to breast cancer has been hypothesized due to the discovery and characterization of a number of high-risk, relatively uncommon genes responsible for the clustering of breast cancer in certain families, which thereafter had a significantly increased risk in comparison with the general population [109, 110]. Many studies suggest that breast cancer susceptibility is transmitted in an autosomal dominant mendelian way [111], but the actual risk of developing breast cancer in a mutation carrier is based on the penetrance of the gene, which consists in the likelihood that the effect (phenotype) of a mutation (genotype) will become clinically apparent.

The BRCA1 gene was firstly identified in 1994 [112] and is localized on the 17th chromosome, whereas the BRCA2 gene was found some years after and is localized on the 13th chromosome [113]. The big size of these genes is important in the context of genetic testing because of the increased probability of mutations and the consequent technically demanding and costly mutations testing, but fortunately the use of modern next generation DNA sequencing is already overcoming these technical and cost issues. Moreover, the BRCA1 gene contains a large number of repetitive elements that facilitate the generation of large deletions and duplications.

BRCA1 is a nuclear protein with two important regions of sequence similarity with known functional motifs: a 42–amino-acid RING (Really Interesting New Gene) domain at the beginning of BRCA1 which binds zinc and is essential in cell growth and differentiation, and the BRCT (breast cancer-1 terminus) motif at the carboxyl terminus, which acts as a phosphoprotein docking motif and a transcriptional activation domain [114, 115]. BRCA2 is also a nuclear protein composed of the following major structural motifs: the eight tandem BRC repeats in the central portion of the protein, which mediates the critical interaction of BRCA2 and RAD51, the TR2 at the carboxyl terminus, which binds RAD51 exists, a single-strand and double-strand DNA binding domain in the C-terminus [113, 116].

Both BRCA1 and BRCA2 genes encode large proteins with multiple functions, which act mainly as tumor suppressor gene products, affecting transcription, cell cycle regulation, genome stability maintenance, and repair of doublestranded DNA breaks for protection of the genome during replication [117, 118]. In particular, BRCA1 prevents replication of damaged DNA by altering chromatin structure and nucleosome organization at the local site of damage, facilitates access by repair complexes, and promotes the use of the error-free repair pathway of homologous recombination-mediated repair rather than the error-prone process of nonhomologous end joining [118]. BRCA2 affects the choice between the two homologous recombination pathways in favor of the error-free one, by interacting with RAD51 [118]. When the wild-type BRCA1 or BRCA2 allele is lost, mutated, or silenced, a high degree of chromosome instability is observed and defective DNA repair may occur, with the consequent accumulation of additional mutations during replication and promotion of carcinogenesis [119].

Mutations in BRCA1 and BRCA2 genes are the most frequent hereditary genetic aberrations in breast cancer and account for approximately half of all hereditary breast cancers. Initial estimates found BRCA1 mutations to be responsible for 45–90% of breast cancer cases in families with apparent autosomal dominant transmission of breast cancer, and this percentage rises if the median age at onset of breast cancer is younger than 45 years [120, 121]. Estimates of BRCA1 and BRCA2 mutation prevalence in unselected patients with breast cancer are in the range of 2–3% [122].

Among BRCA1 mutation carriers, the estimated breast cancer risk is about 65%, the estimated risk of contralateral breast cancer occurrence results 60%, the cumulative risk of ovarian cancer varies between 27 and 45%, and there is also a significantly increased risk of fallopian tube, uterine and cervical cancer, as well as of male breast cancer, stomach, pancreatic, colon and testicular cancer [123, 124, 125, 126].

Among BRCA2 mutation carriers, the estimated lifetime breast cancer risk ranges between 45 and 84%, and that of ovarian cancer between 10 and 20% [123, 127]. There is an increased male breast cancer risk of about 6%, as well as an increased risk of prostate, pancreatic, stomach, gallbladder and bile duct cancers, and malignant melanoma [122, 128].

More than 500 coding region sequence variations have been detected in BRCA1 and 250 in BRCA2. Most unequivocally confirmed mutations reported to date are truncating mutations, adding little in the way of clues for defining functional regions. Although few mutations have been identified in either gene in sporadic breast cancers, a phenotype termed “BRCAness” exist, in which the BRCA1 and BRCA2 proteins act may be somehow disrupted also in sporadic cancer [129]. Finally, there are also some syndromes characterized by an increased breast cancer susceptibility, which are discussed in the following section.

Although germline mutations in BRCA1 and BRCA2 confer a high risk of breast cancer, a great deal of variability has been observed in cancer risk among individuals, both between and within families, as many environmental or genetic factors can modify the penetrance of BRCA1 and BRCA2 mutations. The Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA), analyzing DNA and clinical data from approximately 10,000 BRCA1 and 5000 BRCA2 mutation carriers, demonstrated the role of a number of gene variants in affecting the penetrance in mutation carriers [130].

The most important prognostic modifiers of BRCA1 and BRCA2 mutation carriers are prophylactic oophorectomy and the use of tamoxifen for chemoprevention, which approximately halve the breast cancer risk and decrease the risk of ovarian cancer by about 95% [131, 132].

In comparison with sporadic breast cancers, those related with high-penetrance susceptibility genes correlate with younger age at diagnosis, more aggressive tumor biological behavior, bilaterality, and the eventual coexistence of other cancers in the same individual or in other individuals of the same family, including ovarian, colon, prostate, pancreatic, and endometrial cancers, as well as sarcomas and male breast cancer [133].

Breast cancers arising in BRCA1 mutation carriers are frequently, although not exclusively, basal-like and ER-negative, probably because BRCA1 plays a crucial role in the transcriptional regulation of ER [129, 134]. On the other hand, breast cancer originated in BRCA2 mutation carriers are typically much more similar to sporadic cases, despite with higher grading, higher frequency of ER-positivity and lower frequency of HER2/neu overexpression [135].

Breast cancer prognosis in BRCA1 and BRCA2 mutation carriers is still controversial, and if some authors describe a worse prognosis even in classically low-risk node-negative disease [136], other exclude any significant difference if compared to the general breast cancer population [137]. Furthermore, BRCA1 and BRCA2 mutation carriers result to have an increased risk of contralateral breast cancer occurrence [138].

New drugs have been purposed as a promising therapeutic strategy in BRCA defective tumor cells, such as the inhibitors of the poly(adenosine diphosphate-ribose) polymerase-1 (PARP1), which is an enzyme involved in the single-stranded DNA repair that use base excision repair.

Other breast cancer susceptibility genes have been described, which can be divided into three categories in terms of mutation risk and the frequency of mutation. Along with BRCA1 and BRCA2 gene mutation, the first category includes PTEN and TP53 gene mutations, which are classified as high-penetrance, low-frequency predisposition genes, and the occurrence of even one of these mutations can increase the risk of breast cancer to 25% [139, 140]. The second category includes the CHEK2, ATM, PALB and BRIP1 2 genes, which are moderate-penetrance, low-frequency predisposition genes, and lead to an increased risk of cancer of twofold to fourfold [110]. Finally, the third category consists of the FGFR2, MAP3K1,and TGFB1 gene mutations, which are low-penetrance, high-frequency predisposition genes [141].

5.2. Multigene signatures

In the last decades, many genomic and molecular classification have been described with a prognostic intent. The most famous divides breast cancers into the following subtypes: luminal A, luminal B, HER2-enriched, basal-like, and normal-like [142]. Luminal subtypes express high levels of ER, they usually have an indolent clinical course, with a low distant recurrence rate, which anyway persists even up to 15 years after the diagnosis. Luminal B subtypes express fewer ER-related genes, have a higher proliferation rate and may overexpress HER2/neu, so that they usually require to be treated with both hormonal therapy and chemotherapy. HER2-enriched subtype exhibits HER2/neu gene amplification but does not express ER-related genes, they have an aggressive natural clinical course but fortunately respond very well to HER2-targeted therapy. The basal-like or triple-negative subtype does not express ER, PR, and HER2/neu but expresses basal cytokeratins 5/6 and 17, they have a poor prognosis and a high recurrence rate.

The first molecular signature of breast cancer was determined in 2000 by the expression of a set of genes within the tumor, which were able to predict the clinical outcome [143]. The main limitations of gene signature profiling include difficulties in reproducing the specific gene sets, testing expense, and reporting standardization. However, gene signature cannot be substituted by IHC surrogates which have significant discordances with genetic profiling [144].

The three multigene tests for breast cancer which are commercially available and currently used in the clinical practice are the Oncotype DX test (Genomic Health, Redwood, CA, USA), the MammaPrint test (Netherlands Cancer Institute™ and Agendia™, Netherland), and the Prosigma one (NanoString Technologies, Seattle, WA, USA). The Oncotype DX test is the most widely used molecular test in the therapeutic decision-making, is strongly predictive for endocrine responsiveness in hormone receptor-positive breast cancers with 0–3 positive nodes, and is recommended by both the National Comprehensive Cancer Network (NCCN) and the St. Gallen Consensus [7, 145, 146].

The Oncotype DX is a real-time reverse transcriptase chain reaction (RT-PCR) assay, which measures the expression of a panel of 21 genes in formalin-fixed paraffin-embedded samples, including 16 cancer-related genes (ER, PR, Bcl2, SCUBE2, HER2, GRB7, Ki-67, STK15, survivin, cyclin B1, MYBL2, stromelysin 3, cathepsin L2, GSTM1, CD68, and BAG1) and 5 housekeeping control genes (beta-actin, GAPDH, RPLPO, GUS, and TFRC), to generate a recurrence score to stratify breast cancer patients into three risk groups. The low risk group (score < 18), the intermediate (score 18–30), and the high risk one (score ≥ 31) have a 10-year distant recurrence rate of respectively 6.8, 14.3, and 30.5% [144].

The MammaPrint assay is the second most commonly ordered molecular test approved by the US-FDA and measure the expression of 70 genes involved in the cell cycle, invasion, proliferation, angiogenesis, metastasis, and signal transduction, none of which is tested by the Oncotype DX assay. The MammaPrint customized microarray contains a reduced set of 1900 probes suitable for high-throughput processing, and allows the use of less RNA and a short processing time of 5 days. This assay can be applied in both node-positive and node-negative and both hormone-positive and hormone-negative cancers, it is predictive for responsiveness to chemotherapy and prognostic for early distant recurrence within the first 10 years after diagnosis, which results 13 and 56% respectively in the low- and high-risk group [147, 148, 149].

The Prosigna test is an assay approved by the US-FDA which measures the expression of 50 target genes and 5 constitutively expressed normalization genes, using a proprietary technology called the “nCounter Dx Analysis System.” The assay is highly sensitive and precise and uses 250 ng of RNA from formalin-fixed paraffine-embadded tumor tissue, and generates a risk of recurrence score, which assesses the 10-year risk of distant recurrence for hormone receptor-positive stage I–III breast cancers to be treated with adjuvant endocrine therapy, and correlates to one of the five molecular subtypes previously described [143, 150]. The Prosigna assay results superior to the Oncotype DX test in predicting late distant recurrence after 5–10 years [9, 151].



The authors would like to thank the whole collaborating staff of the Universitât dal Friûl, and the support from Ennergi research non-profit association.


  1. 1. Jemal A, Center MM, De Santis C, Ward EM. Global patterns of cancer incidence and mortality rates and trends. Cancer Epidemiology Biomarkers and Prevention. 2010;19:1893-1907. DOI: 10.1158/1055-9965.epi-10-0437
  2. 2. Bleyer A, Welch HG. Effect of three decades of screening mammography on breast-cancer incidence. The New England Journal of Medicine. 2012;367:1998-2005. DOI: 10.1056/NEJMoa1206809
  3. 3. Driul L, Bernardi S, Bertozzi S, Schiavon M, Londero AP, Petri R. New surgical trends in breast cancer treatment: Conservative interventions and oncoplastic breast surgery. Minerva Ginecologica. 2013;65:289-296
  4. 4. Cedolini C, Bertozzi S, Londero AP, Bernardi S, Seriau L, Concina S, et al. Type of breast cancer diagnosis, screening, and survival. Clinical Breast Cancer. 2014;14:235-240. DOI: 10.1016/j.clbc.2014.02.004
  5. 5. Esserman LJ, Thompson IM, Reid B. Overdiagnosis and overtreatment in cancer: An opportunity for improvement. Journal of the American Medical Association. 2013;310:797-798. DOI: 10.1001/jama.2013.108415
  6. 6. Katz SJ, Morrow M. Addressing overtreatment in breast cancer: The doctors’ dilemma. Cancer. 2013;119:3584-3588. DOI: 10.1002/cncr.28260
  7. 7. van‘t Veer LJ, Dai H, van de Vijver MJ, He YD, Hart AAM, Mao M, et al. Gene expression profiling predicts clinical outcome of breast cancer. Nature2002; 415:530–536. DOI:10.1038/415530a
  8. 8. Wang Y, Klijn JGM, Zhang Y, Sieuwerts AM, Look MP, Yang F, et al. Gene-expression profiles to predict distant metastasis of lymph-node-negative primary breast cancer. Lancet (London, England). 2005;365:671-679. DOI: 10.1016/S0140-6736(05)17947-1
  9. 9. Naoi Y, Noguchi S. Multi-gene classifiers for prediction of recurrence in breast cancer patients. Breast cancer (Tokyo, Japan). 2016;23:12-18. DOI: 10.1007/s12282-015-0596-9
  10. 10. Harris LN, Ismaila N, McShane LM, Andre F, Collyar DE, Gonzalez-Angulo AM, et al. Use of biomarkers to guide decisions on adjuvant systemic therapy for women with early-stage invasive breast cancer: American Society of Clinical Oncology clinical practice guideline. Journal of Clinical Oncology : Official Journal of the American Society of Clinical Oncology. 2016;34:1134-1150. DOI: 10.1200/JCO.2015.65.2289
  11. 11. Sparano JA, Gray RJ, Makower DF, Pritchard KI, Albain KS, Hayes DF, et al. Prospective validation of a 21-gene expression assay in breast cancer. The New England Journal of Medicine. 2015;373:2005-2014. DOI: 10.1056/NEJMoa1510764
  12. 12. Zumoff B, Fishman J, Bradlow HL, Hellman L. Hormone profiles in hormone-dependent cancers. Cancer Research. 1975;35:3365-3373
  13. 13. Stockwell S. Classics in oncology. George Thomas Beatson, M.D. (1848–1933). CA: A Cancer Journal for Clinicians. 1983;33:105-121
  14. 14. Jensen EV, Jordan VC. The estrogen receptor: a model for molecular medicine. Clinical Cancer Research: An Official Journal of the American Association for Cancer Research. 2003;9:1980-1989
  15. 15. McGuire WL. Current status of estrogen receptors in human breast cancer. Cancer. 1975;36:638-644
  16. 16. Klinge CM. Estrogen receptor interaction with estrogen response elements. Nucleic Acids Research. 2001;29:2905-2919
  17. 17. Helguero LA, Faulds MH, Gustafsson JA, Haldosén LA. Estrogen receptors alfa (ERalpha) and beta (ERbeta) differentially regulate proliferation and apoptosis of the normal murine mammary epithelial cell line HC11. Oncogene. 2005;24:6605-6616. DOI: 10.1038/sj.onc.1208807
  18. 18. Grober OMV, Mutarelli M, Giurato G, Ravo M, Cicatiello L, De Filippo MR, et al. Global analysis of estrogen receptor beta binding to breast cancer cell genome reveals an extensive interplay with estrogen receptor alpha for target gene regulation. BMC Genomics. 2011;12:36. DOI: 10.1186/1471-2164-12-36
  19. 19. Ali S, Coombes RC. Estrogen receptor alpha in human breast cancer: Occurrence and significance. Journal of Mammary Gland Biology and Neoplasia. 2000;5:271-281
  20. 20. Renoir JM, Marsaud V, Lazennec G. Estrogen receptor signaling as a target for novel breast cancer therapeutics. Biochemical Pharmacology. 2013;85:449-465. DOI: 10.1016/j. bcp.2012.10.018
  21. 21. Paruthiyil S, Parmar H, Kerekatte V, Cunha GR, Firestone GL, Leitman DC. Estrogen receptor beta inhibits human breast cancer cell proliferation and tumor formation by causing a G2 cell cycle arrest. Cancer Research. 2004;64:423-428
  22. 22. Matthews J, Gustafsson JA. Estrogen signaling: A subtle balance between ER alpha and ER beta. Molecular Interventions. 2003;3:281-292. DOI: 10.1124/mi.3.5.281
  23. 23. Osborne CK, Schiff R. Estrogen-receptor biology: Continuing progress and therapeutic implications. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2005;23:1616-1622. DOI: 10.1200/JCO.2005.10.036
  24. 24. Métivier R, Penot G, Hübner MR, Reid G, Brand H, Kos M, et al. Estrogen receptor-alpha directs ordered, cyclical, and combinatorial recruitment of cofactors on a natural target promoter. Cell. 2003;115:751-763
  25. 25. Lonard DM, O’malley BW. Nuclear receptor coregulators: Judges, juries, and executioners of cellular regulation. Molecular Cell. 2007;27:691-700. DOI: 10.1016/j. molcel.2007.08.012
  26. 26. Heger Z, Guran R, Zitka O, Beklova M, Adam V, Kizek R. In vitro interactions between 17β-estradiol and DNA result in formation of the hormone-DNA complexes. International Journal of Environmental Research and Public Health. 2014;11:7725-7739. DOI: 10.3390/ijerph110807725
  27. 27. Arnold SF, Obourn JD, Jaffe H, Notides AC. Phosphorylation of the human estrogen receptor by mitogen-activated protein kinase and casein kinase II: Consequence on DNA binding. The Journal of Steroid Biochemistry and Molecular Biology. 1995;55:163-172
  28. 28. Rogatsky I, Trowbridge JM, Garabedian MJ. Potentiation of human estrogen receptor alpha transcriptional activation through phosphorylation of serines 104 and 106 by the cyclin A-CDK2 complex. The Journal of Biological Chemistry. 1999;274:22296-22302
  29. 29. Chen D, Washbrook E, Sarwar N, Bates GJ, Pace PE, Thirunuvakkarasu V, et al. Phosphorylation of human estrogen receptor alpha at serine 118 by two distinct signal transduction pathways revealed by phosphorylation-specific antisera. Oncogene. 2002;21:4921-4931. DOI: 10.1038/sj.onc.1205420
  30. 30. Lee H, Bai W. Regulation of estrogen receptor nuclear export by ligand-induced and p38-mediated receptor phosphorylation. Molecular and Cellular Biology. 2002;22:5835-5845
  31. 31. Joel PB, Smith J, Sturgill TW, Fisher TL, Blenis J, Lannigan DA. pp90rsk1 regulates estrogen receptor-mediated transcription through phosphorylation of Ser-167. Molecular and Cellular Biology. 1998;18:1978-1984
  32. 32. Chen D, Pace PE, Coombes RC, Ali S. Phosphorylation of human estrogen receptor alpha by protein kinase a regulates dimerization. Molecular and Cellular Biology. 1999;19:1002-1015
  33. 33. Cui Y, Zhang M, Pestell R, Curran EM, Welshons WV, Fuqua SAW. Phosphorylation of estrogen receptor alpha blocks its acetylation and regulates estrogen sensitivity. Cancer Research. 2004;64:9199-9208. DOI: 10.1158/0008-5472.CAN-04-2126
  34. 34. Wang RA, Mazumdar A, Vadlamudi RK, Kumar R. P21-activated kinase-1 phosphorylates and transactivates estrogen receptor-alpha and promotes hyperplasia in mammary epithelium. The EMBO Journal. 2002;21:5437-5447
  35. 35. Likhite VS, Stossi F, Kim K, Katzenellenbogen BS, Katzenellenbogen JA. Kinase-specific phosphorylation of the estrogen receptor changes receptor interactions with ligand, deoxyribonucleic acid, and coregulators associated with alterations in estrogen and tamoxifen activity. Molecular Endocrinology (Baltimore, Md). 2006;20:3120–3132. DOI:10.1210/me.2006-0068
  36. 36. Daniel AR, Qiu M, Faivre EJ, Ostrander JH, Skildum A, Lange CA. Linkage of progestin and epidermal growth factor signaling: Phosphorylation of progesterone receptors mediates transcriptional hypersensitivity and increased ligand-independent breast cancer cell growth. Steroids. 2007;72:188-201. DOI: 10.1016/j.steroids.2006.11.009
  37. 37. Herynk MH, Parra I, Cui Y, Beyer A, Wu MF, Hilsenbeck SG, et al. Association between the estrogen receptor alpha A908G mutation and outcomes in invasive breast cancer. Clinical Cancer Research: An Official Journal of the American Association for Cancer Research. 2007;13:3235-3243. DOI: 10.1158/1078-0432.CCR-06-2608
  38. 38. Conway K, Parrish E, Edmiston SN, Tolbert D, Tse CK, Geradts J, et al. The estrogen receptor-alpha A908G (K303R) mutation occurs at a low frequency in invasive breast tumors: Results from a population-based study. Breast Cancer Research: BCR. 2005;7:R871-R880. DOI: 10.1186/bcr1315
  39. 39. Conway K, Parrish E, Edmiston SN, Tolbert D, Tse CK, Moorman P, et al. Risk factors for breast cancer characterized by the estrogen receptor alpha A908G (K303R) mutation. Breast Cancer Research : BCR. 2007;9:R36. doi:10.1186/bcr1731
  40. 40. Wehling M, Lösel R. Non-genomic steroid hormone effects: Membrane or intracellular receptors? The Journal of Steroid Biochemistry and Molecular Biology. 2006;102:180-183. DOI: 10.1016/j.jsbmb.2006.09.016
  41. 41. Boonyaratanakornkit V, McGowan E, Sherman L, Mancini MA, Cheskis BJ, Edwards DP. The role of extranuclear signaling actions of progesterone receptor in mediating progesterone regulation of gene expression and the cell cycle. Molecular Endocrinology (Baltimore, Md). 2007;21:359–375. DOI:10.1210/me.2006-0337
  42. 42. Levin ER, Pietras RJ. Estrogen receptors outside the nucleus in breast cancer. Breast Cancer Research and Treatment. 2008;108:351-361. DOI: 10.1007/s10549-007-9618-4
  43. 43. Song RXD, Zhang Z, Chen Y, Bao Y, Santen RJ. Estrogen signaling via a linear pathway involving insulin-like growth factor I receptor, matrix metalloproteinases, and epidermal growth factor receptor to activate mitogen-activated protein kinase in MCF-7 breast cancer cells. Endocrinology. 2007;148:4091-4101. DOI: 10.1210/en.2007-0240
  44. 44. Stoica GE, Franke TF, Moroni M, Mueller S, Morgan E, Iann MC, et al. Effect of estradiol on estrogen receptor-alpha gene expression and activity can be modulated by the ErbB2/PI 3-K/Akt pathway. Oncogene. 2003;22:7998-8011. DOI: 10.1038/sj.onc.1206769
  45. 45. Schiff R, Massarweh SA, Shou J, Bharwani L, Mohsin SK, Osborne CK. Cross-talk between estrogen receptor and growth factor pathways as a molecular target for overcoming endocrine resistance. Clinical Cancer Research: An Official Journal of the American Association for Cancer Research. 2004;10:331S-336S
  46. 46. Anderson WF, Chatterjee N, Ershler WB, Brawley OW. Estrogen receptor breast cancer phenotypes in the surveillance, epidemiology, and end results database. Breast Cancer Research and Treatment. 2002;76:27-36
  47. 47. Buzdar AU, Vergote I, Sainsbury R. The impact of hormone receptor status on the clinical efficacy of the new-generation aromatase inhibitors: A review of data from first-line metastatic disease trials in postmenopausal women. The Breast Journal. 2004;10:211-217. DOI: 10.1111/j.1075-122X.2004.21320.x
  48. 48. Ravdin PM, Green S, Dorr TM, McGuire WL, Fabian C, Pugh RP, et al. Prognostic significance of progesterone receptor levels in estrogen receptor-positive patients with metastatic breast cancer treated with tamoxifen: Results of a prospective southwest oncology group study. Journal of Clinical Oncology : Official Journal of the American Society of Clinical Oncology. 1992;10:1284-1291. DOI: 10.1200/JCO.1992.10.8.1284
  49. 49. Bardou VJ, Arpino G, Elledge RM, Osborne CK, Clark GM. Progesterone receptor status significantly improves outcome prediction over estrogen receptor status alone for adjuvant endocrine therapy in two large breast cancer databases. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2003;21:1973-1979. DOI: 10.1200/JCO.2003.09.099
  50. 50. Nadji M, Gomez-Fernandez C, Ganjei-Azar P, Morales AR. Immunohistochemistry of estrogen and progesterone receptors reconsidered: Experience with 5,993 breast cancers. American Journal of Clinical Pathology. 2005;123:21-27
  51. 51. Wenger CR, Beardslee S, Owens MA, Pounds G, Oldaker T, Vendely P, et al. DNA ploidy, S-phase, and steroid receptors in more than 127,000 breast cancer patients. Breast Cancer Research and Treatment. 1993;28:9-20
  52. 52. Elledge RM, Fuqua SA, Clark GM, Pujol P, Allred DC, McGuire WL. Prognostic significance of p53 gene alterations in node-negative breast cancer. Breast Cancer Research and Treatment. 1993;26:225-235
  53. 53. Arisio R, Sapino A, Cassoni P, Accinelli G, Cuccorese MC, Mano MP, et al. What modifies the relation between tumour size and lymph node metastases in T1 breast carcinomas? Journal of Clinical Pathology. 2000;53:846-850
  54. 54. Early Breast Cancer Trialists’ Collaborative Group (EBCTCG). Effects of chemotherapy and hormonal therapy for early breast cancer on recurrence and 15-year survival: An overview of the randomised trials. Lancet (London, England). 2005;365:1687-1717. DOI: 10.1016/S0140-6736(05)66544-0
  55. 55. Fisher B, Redmond C, Fisher ER, Caplan R. Relative worth of estrogen or progesterone receptor and pathologic characteristics of differentiation as indicators of prognosis in node negative breast cancer patients: Findings from National Surgical Adjuvant Breast and bowel project protocol B-06. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 1988;6:1076-1087. DOI: 10.1200/JCO.1988.6.7. 1076
  56. 56. Rakha EA, El-Sayed ME, Green AR, Paish EC, Powe DG, Gee J, et al. Biologic and clinical characteristics of breast cancer with single hormone receptor positive phenotype. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2007;25:4772-4778. DOI: 10.1200/JCO.2007.12.2747
  57. 57. Hutchins LF, Green SJ, Ravdin PM, Lew D, Martino S, Abeloff M, et al. Randomized, controlled trial of cyclophosphamide, methotrexate, and fluorouracil versus cyclophosphamide, doxorubicin, and fluorouracil with and without tamoxifen for high-risk, node-negative breast cancer: Treatment results of intergroup protocol INT-0102. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2005;23:8313-8321. DOI: 10.1200/JCO.2005.08.071
  58. 58. Fisher B, Anderson S, Tan-Chiu E, Wolmark N, Wickerham DL, Fisher ER, et al. Tamoxifen and chemotherapy for axillary node-negative, estrogen receptor-negative breast cancer: Findings from National Surgical Adjuvant Breast and bowel project B-23. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2001;19:931-942. DOI: 10.1200/JCO.2001.19.4.931
  59. 59. Dowsett M, Allred C, Knox J, Quinn E, Salter J, Wale C, et al. Relationship between quantitative estrogen and progesterone receptor expression and human epidermal growth factor receptor 2 (HER-2) status with recurrence in the Arimidex, Tamoxifen, alone or in combination trial. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2008;26:1059-1065. DOI: 10.1200/JCO.2007.12. 9437
  60. 60. Early Breast Cancer Trialists’ Collaborative Group. Tamoxifen for early breast cancer: An overview of the randomised trials. Early breast cancer Trialists’ collaborative group. Lancet (London England). 1998;351:1451-1467
  61. 61. Goss PE, Ingle JN, Martino S, Robert NJ, Muss HB, Piccart MJ, et al. Efficacy of letrozole extended adjuvant therapy according to estrogen receptor and progesterone receptor status of the primary tumor: National Cancer Institute of Canada clinical trials group MA.17. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2007;25:2006-2011. DOI: 10.1200/JCO.2006.09.4482
  62. 62. Reinert T, Debiasi M, Bines J, Barrios CH. Trends in progression-free survival (PFS) and time to progression (TTP) over time within first-line aromatase inhibitors trials in hormone receptor-positive advanced breast cancer. Breast Cancer Research and Treatment. 2017. DOI: 10.1007/s10549-017-4593-x
  63. 63. Mouridsen H, Gershanovich M, Sun Y, Perez-Carrion R, Boni C, Monnier A, et al. Phase III study of letrozole versus tamoxifen as first-line therapy of advanced breast cancer in postmenopausal women: Analysis of survival and update of efficacy from the international Letrozole breast cancer group. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2003;21:2101-2109. DOI: 10.1200/JCO.2003.04.194
  64. 64. Hess KR, Pusztai L, Buzdar AU, Hortobagyi GN. Estrogen receptors and distinct patterns of breast cancer relapse. Breast Cancer Research and Treatment. 2003;78:105-118
  65. 65. Kuukasjärvi T, Kononen J, Helin H, Holli K, Isola J. Loss of estrogen receptor in recurrent breast cancer is associated with poor response to endocrine therapy. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 1996;14:2584-2589. DOI: 10.1200/JCO.1996.14.9.2584
  66. 66. Lower EE, Glass EL, Bradley DA, Blau R, Heffelfinger S. Impact of metastatic estrogen receptor and progesterone receptor status on survival. Breast Cancer Research and Treatment. 2005;90:65-70. DOI: 10.1007/s10549-004-2756-z
  67. 67. Sari E, Guler G, Hayran M, Gullu I, Altundag K, Ozisik Y. Comparative study of the immunohistochemical detection of hormone receptor status and HER-2 expression in primary and paired recurrent/metastatic lesions of patients with breast cancer. Medical Oncology (Northwood, London, England). 2011;28:57-63. DOI: 10.1007/s12032-010-9418-2
  68. 68. Arslan C, Sari E, Aksoy S, Altundag K. Variation in hormone receptor and HER-2 status between primary and metastatic breast cancer: Review of the literature. Expert Opinion on Therapeutic Targets. 2011;15:21-30. DOI: 10.1517/14656566.2011.537260
  69. 69. Henry NL, Hayes DF. Can biology trump anatomy? Do all node-positive patients with breast cancer need chemotherapy. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2007;25:2501-2503. DOI: 10.1200/JCO.2007.11. 3290
  70. 70. Martin M, Pienkowski T, Mackey J, Pawlicki M, Guastalla JP, Weaver C, et al. Adjuvant docetaxel for node-positive breast cancer. The New England Journal of Medicine. 2005;352:2302-2313. DOI: 10.1056/NEJMoa043681
  71. 71. Mazouni C, Kau SW, Frye D, Andre F, Kuerer HM, Buchholz TA, et al. Inclusion of taxanes, particularly weekly paclitaxel, in preoperative chemotherapy improves pathologic complete response rate in estrogen receptor-positive breast cancers. Annals of Oncology : Official Journal of the European Society for Medical Oncology. 2007;18:874-880. DOI: 10.1093/annonc/mdm008
  72. 72. Nofech-Mozes S, Vella ET, Dhesy-Thind S, Hagerty KL, Mangu PB, Temin S, et al. Systematic review on hormone receptor testing in breast cancer. Applied Immunohistochemistry and Molecular Morphology: AIMM. 2012;20:214-263. DOI: 10.1097/PAI.0b013e318234aa12
  73. 73. Hammond MEH, Hayes DF, Dowsett M, Allred DC, Hagerty KL, Badve S, et al. American Society of Clinical Oncology/college of American pathologists guideline recommendations for immunohistochemical testing of estrogen and progesterone receptors in breast cancer. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2010;28:2784-2795. DOI: 10.1200/JCO.2009.25.6529
  74. 74. Press MF, Cordon-Cardo C, Slamon DJ. Expression of the HER-2/neu proto-oncogene in normal human adult and fetal tissues. Oncogene. 1990;5:953-962
  75. 75. Yarden Y, Pines G. The ERBB network: At last, cancer therapy meets systems biology. Nature Reviews Cancer. 2012;12:553-563. DOI: 10.1038/nrc3309
  76. 76. Oh JJ, Grosshans DR, Wong SG, Slamon DJ. Identification of differentially expressed genes associated with HER-2/neu overexpression in human breast cancer cells. Nucleic Acids Research. 1999;27:4008-4017
  77. 77. Slamon DJ, Godolphin W, Jones LA, Holt JA, Wong SG, Keith DE, et al. Studies of the HER-2/neu proto-oncogene in human breast and ovarian cancer. Science (New York, N.Y.). 1989;244:707-712
  78. 78. Slamon DJ, Clark GM, Wong SG, Levin WJ, Ullrich A, McGuire WL. Human breast cancer: Correlation of relapse and survival with amplification of the HER-2/neu oncogene. Science (New York, N.Y.). 1987;235:177-182
  79. 79. Saffari B, Jones LA, el Naggar A, Felix JC, George J, Press MF. Amplification and overexpression of HER-2/neu (c-erbB2) in endometrial cancers: Correlation with overall survival. Cancer Research. 1995;55:5693-5698
  80. 80. Press MF, Pike MC, Hung G, Zhou JY, Ma Y, George J, et al. Amplification and overexpression of HER-2/neu in carcinomas of the salivary gland: Correlation with poor prognosis. Cancer Research. 1994;54:5675-5682
  81. 81. Park JB, Rhim JS, Park SC, Kimm SW, Kraus MH. Amplification, overexpression, and rearrangement of the erbB-2 protooncogene in primary human stomach carcinomas. Cancer Research. 1989;49:6605-6609
  82. 82. Sorkin A, Goh LK. Endocytosis and intracellular trafficking of ErbBs. Experimental Cell Research. 2008;314:3093-3106. DOI: 10.1016/j.yexcr.2008.08.013
  83. 83. Wolff AC, Hammond MEH, Hicks DG, Dowsett M, McShane LM, Allison KH, et al. Recommendations for human epidermal growth factor receptor 2 testing in breast cancer: American Society of Clinical Oncology/College of American Pathologists clinical practice guideline update. Archives of Pathology and Laboratory Medicine. 2014;138:241-256. DOI: 10.5858/arpa.2013-0953-SA
  84. 84. Press MF, Bernstein L, Thomas PA, Meisner LF, Zhou JY, Ma Y, et al. HER-2/neu gene amplification characterized by fluorescence in situ hybridization: Poor prognosis in node-negative breast carcinomas. Journal of Clinical Oncology : Official Journal of the American Society of Clinical Oncology. 1997;15:2894-2904. DOI: 10.1200/JCO.1997.15.8. 2894
  85. 85. Mass RD, Press MF, Anderson S, Cobleigh MA, Vogel CL, Dybdal N, et al. Evaluation of clinical outcomes according to HER2 detection by fluorescence in situ hybridization in women with metastatic breast cancer treated with trastuzumab. Clinical Breast Cancer. 2005;6:240-246. DOI: 10.3816/CBC.2005.n.026
  86. 86. Seidman AD, Berry D, Cirrincione C, Harris L, Muss H, Marcom PK, et al. Randomized phase III trial of weekly compared with every-3-weeks paclitaxel for metastatic breast cancer, with trastuzumab for all HER-2 overexpressors and random assignment to trastuzumab or not in HER-2 nonoverexpressors: Final results of cancer and leukemia group B protocol 9840. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2008;26:1642-1649. DOI: 10.1200/JCO.2007.11.6699
  87. 87. Slamon D, Eiermann W, Robert N, Pienkowski T, Martin M, Press M, et al. Adjuvant Trastuzumab in HER2-positive breast cancer. The New England Journal of Medicine. 2011;365:1273-1283. DOI: 10.1056/NEJMoa0910383
  88. 88. Geyer CE, Forster J, Lindquist D, Chan S, Romieu CG, Pienkowski T, et al. Lapatinib plus Capecitabine for HER2-positive advanced breast cancer. The New England Journal of Medicine. 2006;355:2733-2743. DOI: 10.1056/NEJMoa064320
  89. 89. Baselga J, Cortés J, Kim SB, Im SA, Hegg R, Im YH, et al. Pertuzumab plus Trastuzumab plus docetaxel for metastatic breast cancer. The New England Journal of Medicine. 2012;366:109-119. DOI: 10.1056/NEJMoa1113216
  90. 90. Verma S, Miles D, Gianni L, Krop IE, Welslau M, Baselga J, et al. Trastuzumab Emtansine for HER2-positive advanced breast cancer. The New England Journal of Medicine. 2012;367:1783-1791. DOI: 10.1056/NEJMoa1209124
  91. 91. Dati C, Antoniotti S, Taverna D, Perroteau I, De Bortoli M. Inhibition of c-erbB-2 oncogene expression by estrogens in human breast cancer cells. Oncogene. 1990;5:1001-1006
  92. 92. Pietras RJ, Arboleda J, Reese DM, Wongvipat N, Pegram MD, Ramos L, et al. HER-2 tyrosine kinase pathway targets estrogen receptor and promotes hormone-independent growth in human breast cancer cells. Oncogene. 1995;10:2435-2446
  93. 93. Ellis MJ, Coop A, Singh B, Mauriac L, Llombert-Cussac A, Jänicke F, et al. Letrozole is more effective neoadjuvant endocrine therapy than tamoxifen for ErbB-1- and/or ErbB-2-positive, estrogen receptor-positive primary breast cancer: Evidence from a phase III randomized trial. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2001;19:3808-3816. DOI: 10.1200/JCO.2001.19.18.3808
  94. 94. Gennari A, Sormani MP, Pronzato P, Puntoni M, Colozza M, Pfeffer U, et al. HER2 status and efficacy of adjuvant anthracyclines in early breast cancer: A pooled analysis of randomized trials. Journal of the National Cancer Institute. 2008;100:14-20. DOI: 10. 1093/jnci/djm252
  95. 95. Hayes DF, Thor AD, Dressler LG, Weaver D, Edgerton S, Cowan D, et al. HER2 and response to paclitaxel in node-positive breast cancer. The New England Journal of Medicine. 2007;357:1496-1506. DOI: 10.1056/NEJMoa071167
  96. 96. Wolff AC, Hammond MEH, Schwartz JN, Hagerty KL, Allred DC, Cote RJ, et al. American Society of Clinical Oncology/College of American pathologists guideline recommendations for human epidermal growth factor receptor 2 testing in breast cancer. Archives of Pathology and Laboratory Medicine. 2007;131:18-43. DOI: 10.1043/1543-2165(2007)131[18:ASOCCO]2.0.CO;2
  97. 97. Press MF, Slamon DJ, Flom KJ, Park J, Zhou JY, Bernstein L. Evaluation of HER-2/neu gene amplification and overexpression: Comparison of frequently used assay methods in a molecularly characterized cohort of breast cancer specimens. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2002;20:3095-3105. DOI: 10.1200/JCO.2002.09.094
  98. 98. Penault-Llorca F, Bilous M, Dowsett M, Hanna W, Osamura RY, Rüschoff J, et al. Emerging technologies for assessing HER2 amplification. American Journal of Clinical Pathology. 2009;132:539-548. DOI: 10.1309/AJCPV2I0HGPMGBSQ
  99. 99. Colozza M, Azambuja E, Cardoso F, Sotiriou C, Larsimont D, Piccart MJ. Proliferative markers as prognostic and predictive tools in early breast cancer: Where are we now? Annals of Oncology: Official Journal of the European society for Medical Oncology. 2005;16:1723-1739. DOI: 10.1093/annonc/mdi352
  100. 100. Baak JPA, van Diest PJ, Janssen EAM, Gudlaugsson E, Voorhorst FJ, van der Wall E, et al. Proliferation accurately identifies the high-risk patients among small, low-grade, lymph node-negative invasive breast cancers. Annals of Oncology: Official Journal of the European Society for Medical Oncology. 2008;19:649-654. DOI: 10.1093/annonc/mdm535
  101. 101. Harris L, Fritsche H, Mennel R, Norton L, Ravdin P, Taube S, et al. American Society of Clinical Oncology 2007 update of recommendations for the use of tumor markers in breast cancer. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2007;25:5287-5312. DOI: 10.1200/JCO.2007.14.2364
  102. 102. Dowsett M, Smith IE, Ebbs SR, Dixon JM, Skene A, A’Hern R, et al. Prognostic value of Ki67 expression after short-term presurgical endocrine therapy for primary breast cancer. Journal of the National Cancer Institute. 2007;99:167-170. DOI: 10.1093/jnci/djk020
  103. 103. Fasching PA, Heusinger K, Haeberle L, Niklos M, Hein A, Bayer CM, et al. Ki67, chemotherapy response, and prognosis in breast cancer patients receiving neoadjuvant treatment. BMC Cancer. 2011;11:486. DOI: 10.1186/1471-2407-11-486
  104. 104. Ellis MJ, Suman VJ, Hoog J, Lin L, Snider J, Prat A, et al. Randomized phase II neoadjuvant comparison between letrozole, anastrozole, and exemestane for postmenopausal women with estrogen receptor-rich stage 2 to 3 breast cancer: Clinical and biomarker outcomes and predictive value of the baseline PAM50-based intrinsic subtype–ACOSOG Z1031. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology. 2011;29:2342-2349. DOI: 10.1200/JCO.2010.31.6950
  105. 105. Fisher B, Dignam J, Wolmark N, DeCillis A, Emir B, Wickerham DL, et al. Tamoxifen and chemotherapy for lymph node-negative, estrogen receptor-positive breast cancer. Journal of the National Cancer Institute. 1997;89:1673-1682
  106. 106. Bedard PL, Cardoso F. Can some patients avoid adjuvant chemotherapy for early-stage breast cancer? Nature Reviews Clinical Oncology. 2011;8:272-279. DOI: 10.1038/nrclinonc. 2011.19
  107. 107. Golub TR. Molecular classification of cancer: Class discovery and class prediction by gene expression monitoring. Science. 1999;286:531-537. DOI: 10.1126/science.286.5439. 531
  108. 108. van de, Vijver MJ, He YD, van’t Veer LJ, Dai H, Hart AAM, Voskuil DW, et al. A gene-expression signature as a predictor of survival in breast cancer. The New England Journal of Medicine. 2002;347:1999-2009. DOI: 10.1056/NEJMoa021967
  109. 109. Williams WR, Anderson DE. Genetic epidemiology of breast cancer: Segregation analysis of 200 Danish pedigrees. Genetic Epidemiology. 1984;1:7-20. DOI: 10.1002/gepi. 1370010104
  110. 110. Stratton MR, Rahman N. The emerging landscape of breast cancer susceptibility. Nature Genetics. 2008;40:17-22. DOI: 10.1038/ng.2007.53
  111. 111. Newman B, Austin MA, Lee M, King MC. Inheritance of human breast cancer: Evidence for autosomal dominant transmission in high-risk families. Proceedings of the National Academy of Sciences of the United States of America. 1988;85:3044-3048
  112. 112. Miki Y, Swensen J, Shattuck-Eidens D, Futreal PA, Harshman K, Tavtigian S, et al. A strong candidate for the breast and ovarian cancer susceptibility gene BRCA1. Science (New York, NY). 1994;266:66-71
  113. 113. Wooster R, Bignell G, Lancaster J, Swift S, Seal S, Mangion J, et al. Identification of the breast cancer susceptibility gene BRCA2. Nature. 1995;378:789-792. DOI: 10.1038/378789a0
  114. 114. Kerr P, Ashworth A. New complexities for BRCA1 and BRCA2. Current Biology: CB. 2001;11:R668-R676
  115. 115. Leung CCY, Glover JNM. BRCT domains: Easy as one, two, three. Cell Cycle (Georgetown, Tex). 2011;10:2461-2470. DOI: 10.4161/cc.10.15.16312
  116. 116. Esashi F, Galkin VE, Yu X, Egelman EH, West SC. Stabilization of RAD51 nucleoprotein filaments by the C-terminal region of BRCA2. Nature Structural and Molecular Biology. 2007;14:468-474. DOI: 10.1038/nsmb1245
  117. 117. Venkitaraman AR. Cancer susceptibility and the functions of BRCA1 and BRCA2. Cell. 2002;108:171-182
  118. 118. Lord CJ, Ashworth A. The DNA damage response and cancer therapy. Nature. 2012;481:287-294. DOI: 10.1038/nature10760
  119. 119. Tutt ANJ, Lord CJ, McCabe N, Farmer H, Turner N, Martin NM, et al. Exploiting the DNA repair defect in BRCA mutant cells in the design of new therapeutic strategies for cancer. Cold Spring Harbor Symposia on Quantitative Biology. 2005;70:139-148. DOI: 10. 1101/sqb.2005.70.012
  120. 120. Narod SA, Feunteun J, Lynch HT, Watson P, Conway T, Lynch J, et al. Familial breast-ovarian cancer locus on chromosome 17q12-q23. Lancet (London, England). 1991;338:82-83
  121. 121. Easton DF, Bishop DT, Ford D, Crockford GP. Genetic linkage analysis in familial breast and ovarian cancer: Results from 214 families. The breast cancer linkage consortium. American Journal of Human Genetics. 1993;52:678-701
  122. 122. Wooster R, Weber BL. Breast and ovarian cancer. The New England Journal of Medicine. 2003;348:2339-2347. DOI: 10.1056/NEJMra012284
  123. 123. Antoniou A, Pharoah PDP, Narod S, Risch HA, Eyfjord JE, Hopper JL, et al. Average risks of breast and ovarian cancer associated with BRCA1 or BRCA2 mutations detected in case series unselected for family history: A combined analysis of 22 studies. American Journal of Human Genetics. 2003;72:1117-1130. DOI: 10.1086/375033
  124. 124. Brose MS, Rebbeck TR, Calzone KA, Stopfer JE, Nathanson KL, Weber BL. Cancer risk estimates for BRCA1 mutation carriers identified in a risk evaluation program. Journal of the National Cancer Institute. 2002;94:1365-1372
  125. 125. Whittemore AS, Gong G, Itnyre J. Prevalence and contribution of BRCA1 mutations in breast cancer and ovarian cancer: Results from three U.S. population-based case-control studies of ovarian cancer. American Journal of Human Genetics. 1997;60:496-504
  126. 126. Ford D, Easton DF, Bishop DT, Narod SA, Goldgar DE. Risks of cancer in BRCA1-mutation carriers. Breast Cancer Linkage Consortium. Lancet (London, England). 1994;343:692-695
  127. 127. Ford D, Easton DF, Stratton M, Narod S, Goldgar D, Devilee P, et al. Genetic heterogeneity and penetrance analysis of the BRCA1 and BRCA2 genes in breast cancer families. The Breast Cancer Linkage Consortium. American Journal of Human Genetics. 1998;62:676-689
  128. 128. Breast Cancer Linkage Consortium. Cancer risks in BRCA2 mutation carriers. Journal of the National Cancer Institute. 1999;91:1310-1316
  129. 129. Turner N, Tutt A, Ashworth A. Hallmarks of ‘BRCAness’ in sporadic cancers. Nature Reviews Cancer. 2004;4:814-819. DOI: 10.1038/nrc1457
  130. 130. Chenevix-Trench G, Milne RL, Antoniou AC, Couch FJ, Easton DF, Goldgar DE, et al. An international initiative to identify genetic modifiers of cancer risk in BRCA1 and BRCA2 mutation carriers: The consortium of investigators of modifiers of BRCA1 and BRCA2 (CIMBA). Breast Cancer Research: BCR. 2007;9:104. DOI: 10.1186/bcr1670
  131. 131. Gronwald J, Tung N, Foulkes WD, Offit K, Gershoni R, Daly M, et al. Tamoxifen and contralateral breast cancer in BRCA1 and BRCA2 carriers: An update. International Journal of Cancer. 2006;118:2281-2284. DOI: 10.1002/ijc.21536
  132. 132. Domchek SM, Friebel TM, Neuhausen SL, Wagner T, Evans G, Isaacs C, et al. Mortality after bilateral salpingo-oophorectomy in BRCA1 and BRCA2 mutation carriers: A prospective cohort study. The Lancet Oncology. 2006;7:223-229. DOI: 10.1016/S1470-2045(06)70585-X
  133. 133. Lakhani SR, Gusterson BA, Jacquemier J, Sloane JP, Anderson TJ, van de, Vijver MJ, et al. The pathology of familial breast cancer: Histological features of cancers in families not attributable to mutations in BRCA1 or BRCA2. Clinical Cancer Research: An Official Journal of the American Association for Cancer Research. 2000;6:782-789
  134. 134. Hosey AM, Gorski JJ, Murray MM, Quinn JE, Chung WY, Stewart GE, et al. Molecular basis for estrogen receptor alpha deficiency in BRCA1-linked breast cancer. Journal of the National Cancer Institute. 2007;99:1683-1694. DOI: 10.1093/jnci/djm207
  135. 135. Bane AL, Beck JC, Bleiweiss I, Buys SS, Catalano E, Daly MB, et al. BRCA2 mutation-associated breast cancers exhibit a distinguishing phenotype based on morphology and molecular profiles from tissue microarrays. The American Journal of Surgical Pathology. 2007;31:121-128. DOI: 10.1097/01.pas.0000213351.49767.0f
  136. 136. Moller P, Evans DG, Reis MM, Gregory H, Anderson E, Maehle L, et al. Surveillance for familial breast cancer: Differences in outcome according to BRCA mutation status. International Journal of Cancer. 2007;121:1017-1020. DOI: 10.1002/ijc.22789
  137. 137. Rennert G, Bisland-Naggan S, Barnett-Griness O, Bar-Joseph N, Zhang S, Rennert HS, et al. Clinical outcomes of breast cancer in carriers of BRCA1 and BRCA2 mutations. The New England Journal of Medicine. 2007;357:115-123. DOI: 10.1056/NEJMoa070608
  138. 138. Liebens FP, Carly B, Pastijn A, Rozenberg S. Management of BRCA1/2 associated breast cancer: A systematic qualitative review of the state of knowledge in 2006. European Journal of Cancer (Oxford, England: 1990). 2007;43:238-257. DOI: 10.1016/j.ejca.2006.07. 019
  139. 139. Gayther SA, Pharoah PD, Ponder BA. The genetics of inherited breast cancer. Journal of Mammary Gland Biology and Neoplasia. 1998;3:365-376
  140. 140. Nathanson KL, Wooster R, Weber BL, Nathanson KN. Breast cancer genetics: What we know and what we need. Nature Medicine. 2001;7:552-556. DOI: 10.1038/87876
  141. 141. Hirshfield KM, Rebbeck TR, Levine AJ. Germline mutations and polymorphisms in the origins of cancers in women. Journal of Oncology. 2010;2010:297671. DOI: 10.1155/2010/297671
  142. 142. Goldhirsch A, Wood WC, Coates AS, Gelber RD, Thürlimann B, Senn HJ, et al. Strategies for subtypes–dealing with the diversity of breast cancer: Highlights of the St. Gallen international expert consensus on the primary therapy of early breast cancer 2011. Annals of Oncology: Official Journal of the European Society for Medical Oncology. 2011;22:1736-1747. DOI: 10.1093/annonc/mdr304
  143. 143. Sørlie T, Perou CM, Tibshirani R, Aas T, Geisler S, Johnsen H, et al. Gene expression patterns of breast carcinomas distinguish tumor subclasses with clinical implications. Proceedings of the National Academy of Sciences of the United States of America. 2001;98:10869-10874. DOI: 10.1073/pnas.191367098
  144. 144. Paik S, Shak S, Tang G, Kim C, Baker J, Cronin M, et al. A multigene assay to predict recurrence of tamoxifen-treated, node-negative breast cancer. The New England Journal of Medicine. 2004;351:2817-2826. DOI: 10.1056/NEJMoa041588
  145. 145. Albain KS, Barlow WE, Shak S, Hortobagyi GN, Livingston RB, Yeh IT, et al. Prognostic and predictive value of the 21-gene recurrence score assay in postmenopausal women with node-positive, oestrogen-receptor-positive breast cancer on chemotherapy: A retrospective analysis of a randomised trial. The Lancet Oncology. 2010;11:55-65. DOI: 10.1016/S1470-2045(09)70314-6
  146. 146. Gnant M, Harbeck N, St TC. Gallen 2011: Summary of the consensus discussion. Breast care (Basel, Switzerland). 2011;6:136-141. DOI: 10.1159/000328054
  147. 147. Buyse M, Loi S, van’t Veer L, Viale G, Delorenzi M, Glas AM, et al. Validation and clinical utility of a 70-gene prognostic signature for women with node-negative breast cancer. Journal of the National Cancer Institute. 2006;98:1183-1192. DOI: 10.1093/jnci/djj329
  148. 148. Viale G, de, Snoo FA, Slaets L, Bogaerts J, van ‘t Veer L, Rutgers EJ, et al. Immunohistochemical versus molecular (BluePrint and MammaPrint) subtyping of breast carcinoma. Outcome results from the EORTC 10041/BIG 3-04 MINDACT trial. Breast Cancer Research and Treatment. 2017. DOI: 10.1007/s10549-017-4509-9
  149. 149. Aalders KC, Kuijer A, Straver ME, Slaets L, Litiere S, Viale G, et al. Characterisation of multifocal breast cancer using the 70-gene signature in clinical low-risk patients enrolled in the EORTC 10041/BIG 03-04 MINDACT trial. European Journal of Cancer (Oxford, England : 1990). 2017;79:98-105. DOI: 10.1016/j.ejca.2017.03.034
  150. 150. Chia SK, Bramwell VH, Tu D, Shepherd LE, Jiang S, Vickery T, et al. A 50-gene intrinsic subtype classifier for prognosis and prediction of benefit from adjuvant tamoxifen. Clinical Cancer Research : An Official Journal of the American Association for Cancer Research. 2012;18:4465-4472. DOI: 10.1158/1078-0432.CCR-12-0286
  151. 151. Martín M, González-Rivera M, Morales S, de la Haba-Rodriguez J, González-Cortijo L, Manso L, et al. prospective study of the impact of the Prosigna assay on adjuvant clinical decision-making in unselected patients with estrogen receptor positive, human epidermal growth factor receptor negative, node negative early-stage breast cancer. Current Medical Research and Opinion. 2015;31:1129-1137. DOI: 10.1185/03007995.2015. 1037730

Written By

Serena Bertozzi, Ambrogio P Londero, Luca Seriau, Roberta Di Vora, Carla Cedolini and Laura Mariuzzi

Submitted: 15 October 2017 Reviewed: 18 April 2018 Published: 05 November 2018