A case of 77-year-old female with an invasive lobular carcinoma with extracellular mucin is presented. She felt palpable mass in her left breast. Then, she came to our hospital for further examination. Mammography of right in full view revealed architectural distortion in left upper portion. And ultrasonography demonstrated low-echoic mass about 2 cm in diameter and invasion of the fat tissue was observed. Hence, malignancy was suspected and magnetic resonance imaging (MRI) was performed. MRI findings showed irregular shaped and margined mass with small T2-high-signal intensity. These findings suggested invasive carcinoma with mucin. Because the cancer lesion was not large, partial mastectomy was performed. Interestingly, pathological diagnosis was invasive lobular carcinoma with extracellular mucin. Extracellular mucinous lesion was concordant with small T2-high-signal intensity. This type of carcinoma was previously reported only in three cases, and rare but important, because the treatment and prognosis might change by histological subtypes. We suggest one of the MRI special features of our case is not only irregular shaped and margined mass but also small T2-high-signal intensity. These MR findings might be one of the valuable findings for the diagnosis and differentiation between this type of carcinoma from other tumors.
Part of the book: Breast Imaging