Ovarian cancers remain a perplexing group of diseases that continue to raise questions over their etiology and clinical behavior. They are the most fatal of gynecological cancers. Despite a global lifetime risk of only 1–2%, they contribute the highest mortality and the lowest 5-year (overall) survival rate of just 35%. The three broad histological groups: epithelial, sex cord-stromal and germ cell cancers have different biologic behavior and may constitute different clinical disease entities. Of the eight subtypes in the epithelial group, high-grade serous are universally the most common and have the worst prognosis. Globally making 65–85% of all ovarian cancers, most of the focus on risk factors has been directed on the epithelial group but the importance of other primary malignancies cannot be overemphasized as a step towards understanding their etiology and clinical behavior. The normal ovary has none of the epithelia that produce the range of epithelial ovarian cancers or there is an obvious premalignant stage, symptoms are very vague, screening and early diagnosis are difficult and indeed unrewarding. No specific etiology is known for any of the histologic groups. However, commonly mentioned risk factors like increasing age, genetics, nulliparity, prolonged infertility, use of fertility drugs, high animal fat, obesity, endometriosis, polycystic ovary syndrome, previous history of cancer, use of hormone replacement therapy, pelvic inflammatory disease and smoking may not apply to all the subtypes, while factors like increasing parity, breast feeding, use of oral contraceptive pills, hysterectomy, tubal ligation and use of antioxidants may differ in the degree of protection they provide. There may also be geographical and probably racial variations in the relevance of some of the risk factors. Thorough understanding of the predisposing and protective factors of the various histologic subtypes is an important step understanding the disease and therefore improving treatment outcome or providing effective prevention.
Part of the book: Tumor Progression and Metastasis