Apocrine carcinoma of the breast.

Apocrine carcinoma is a rare variant of breast carcinoma, and accounts for 0.3 to 1.0% of all breast cancers. A 55-year-old Japanese female patient presented with a right breast tumor, which had been detected by mass-screening, and she was admitted to our hospital. The physical examination revealed an elastic hard lump in the upper lateral quadrant of the right breast. The tumor size was approximately 1.0 cm in diameter, and the border was clear. There were no palpable axillary lymph nodes nor supraclavicular nodes. Fine-needle aspiration cytology revealed invasive ductal carcinoma. The patient underwent a partial resection of the right breast (breast conserving therapy) and a right axillary lymphadenectomy. Macroscopically, the resected specimen revealed a white tumor measuring 1.2 x 1.2 x 1.0 cm. The TNM classification was diagnosed as T1cN0M0 stage I. Histopathologically, the tumor revealed a proliferation of atypical epithelial cells with apocrine differentiation, arranged in a papillotubular or cribriform growth pattern with stromal invasion. The tumor cells showed irregular round-shaped nuclei often containing prominent nucleoli, and had particularly abundant eosinophilic granular cytoplasm. In the immunohistochemical analysis, these carcinoma cells were positive for Gross Cystic Disease Fluid Protein 15 and the androgen receptor, whereas they were negative for the estrogen and progesterone receptors. Immunohistochemical staining for Her2 using the HercepTest was found to be negative (score 0). Thus, the pathological diagnosis was apocrine carcinoma. There were no metastases in the axillary lymph nodes. The patient has had no recurrence in 8 years after surgery.