CASE REPORT Primary acinic cell carcinoma of the breast

A49 year old woman presented with a lump in her right breast, which was partially cystic, and after draining refilled immediately. A biopsy showed an infiltrating ductal carcinoma grade 3, with the additional feature of unusual cytoplasmic granules. Several courses of cytotoxic chemotherapy were administered which included adriamycin, cyclophosphamide, methotrexate, and 5 fluorouracil. Eight months later the patient underwent mastectomy. A liver ultrasound showed what appeared to be peripherally located cysts, which were too small to biopsy and were considered to be simple cysts. Twelve months later she had massive hepatomegaly as a result of metastases for which she received additional courses of chemotherapy including mitozantrone, mitomycin c, and methotrexate. In addition, she was treated with epirubicin but her liver enlargement continued. Infusional treatment was given but she continued to deteriorate and died three years after her initial diagnosis. The first biopsy consisted of a piece of tissue measuring 4 × 4.6 × 0.3 cm. Microscopic examination revealed an infiltrating ductal carcinoma grade 3 composed of cells arranged in small tightly packed solid nests and tubular structures. Areas composed of larger solid nests were also noted. The cells showed prominent nuclear pleomorphism with numerous mitotic figures (up to 13/single high power field especially in solid nests). However, the most striking feature was the presence in most of the cells of small and large, brightly eosinophilic cytoplasmic granules (fig 1). Small numbers of cells displayed clear or vacuolated cytoplasm. Secretory material showing less intense eosinophilia was present in many of the tubular structures. Foci of vascular invasion were also present. In the mastectomy specimen there was an irregular firm area measuring 2 cm in its maximum dimension. Sections taken from the mastectomy specimen showed patchy residual foci of infiltrating carcinoma. The cells were arranged in small groups and tightly packed tubular structures without the previously described large solid areas. Many of the cells contained clear or multivacuolated cytoplasm, which at times resembled lipoblasts (fig 2). In some areas the cells had intensely eosinophilic cytoplasm. Although some granular cells were present granularity was much less obvious in most cells. This was in contrast to the first biopsy which was composed predominantly of granular cells. Vascular invasion was also present but mitotic activity was low. There were single cells scattered throughout the stroma, a feature sometimes seen after cytotoxic treatment, and some of these cells displayed prominent cytoplasmic granularity. Two of 11 lymph nodes contained small subcapsular metastatic deposits. These cells also showed prominent brightly eosinophilic cytoplasm with greatly diminished granularity. The eosinophilic secretory material was periodic acid Schiff diastase resistant, as were the cytoplasmic granules. The granules were strongly positive with antibodies to salivary amylase, lysozyme, α1 anti-chymotrypsin and α1 anti-trypsin, with fewer numbers of cells staining in the postchemotherapy mastectomy specimen. They were negative for glial fibrillary acidic protein, gross cystic disease fluid protein 15, chromogranin, and synaptophysin. S100 protein showed focal cytoplasmic positivity. A phloxine tartrazine stain for Paneth cell granules was negative. Electron microscopy performed on formalin fixed tissue taken from both specimens demonstrated numerous cytoplasmic electron dense granules of varying size consistent with acinic cell granules (fig 3), and prominent rough endoplasmic reticulum. In addition, many of the cells from the mastectomy specimen contained very few Figure 1 Invasive carcinoma with numerous large and small eosinophilic cytoplasmic granules. Original magnification, ×100.