Acinic cell carcinoma of the breast is an extremely rare,
malignant neoplasm characterized by widespread acinar cell-like differentiation and clinically low-grade
malignancy. Herein, we report a case of
acinic cell carcinoma of the breast in a 41-year-old woman. The
tumor was poorly demarcated but had a firm consistency. It was removed with
lumpectomy, and sentinel lymph node biopsy was performed to check for
metastasis. Microscopically, the
tumor showed an infiltrative growth pattern with a combination of solid, trabecular, and microglandular areas. Many of the
tumor cells had abundant clear vacuolated cytoplasm containing
zymogen-typed granules which resemble acinar cells of the salivary glands. The immunohistochemical profile of the
tumor was also similar to that of salivary gland
acinic cell carcinoma: the
tumor cells were positive for
amylase,
lysozyme, α -1-antichymotrypsin,
S-100 protein, and
epithelial membrane antigen and negative for
estrogen receptor,
progesterone receptor, and
human epidermal growth factor receptor 2. She received postoperative chemoradiation
therapy and has been well for 3 years since surgery. As studies on large series are lacking, further studies are needed to elucidate the
biological characteristics of
acinic cell carcinoma of the breast.