The first case of acinic cell carcinoma of the breast within a fibroadenoma: case report.

A case of acinic cell carcinoma of the breast is reported in a 26-year-old woman. She presented a lump in her right breast, that seemed to be a fibroadenoma. The open biopsy revealed a well-bordered fibroadenoma, together with a proliferation of cells characterized by serous acinar differentiation and eosinophilic cytoplasmic granules. Tumor cells stained for amylase, lysozyme, α-1-antichymotripsin, epithelial membrane antigen, S-100 protein, pan-cytokeratin, cytokeratin 7 and E-cadherin. Estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 overexpression, CD10, P63, smooth muscle actin, cytokeratin 5/6 were negative. The sentinel node was negative. 8 months after surgery she is in good clinical conditions without recurrence or metastases.