High grade acinic cell carcinoma of the breast with clear cytoplasm mimics clear cell carcinoma in a BRCA1 mutation carrier: a case report and review of the literature on the molecular analysis.

Acinic cell carcinoma of the breast is an extremely rare tumor. To the best of our knowledge, only one case is reported to have bilateral tumors and had both BRCA1 and TP53 mutation. Herein, we report another case of acinic cell carcinoma of the breast in a 29-years-old female carrying germline BRCA1 and TP53 mutation, and the tumor showed a complex combination of histological features which had not only the reported common features such as diffuse infiltrative small acinar or glandular structures mixed with solid nests, but also the uncommon widespread clear cells, high grade tumor cells. The immunohistochemical profile of the tumor cells was strongly positive for lysozyme and triple negative for ER, PR, HER2. Although she had bilateral high grade breast cancers, this patient refused postoperative adjuvant therapy this time and has been doing well in the past 12 months. As a rare form of triple-negative breast cancer with a relatively not so bad prognosis, more reports are needed to understand its biological characteristics.