Paneth cell-like eosinophilic cytoplasmic granules in breast carcinoma

Prominent coarse eosinophilic cytoplasmic granules reminiscent of those in intestinal Paneth cells are rarely identified in breast carcinomas. In the literature, this phenomenon seems to be associated with acinic cell carcinoma of the breast or microglandular adenosis-related lesions. In this study, we report 3 breast carcinoma cases with such granules. Two of the cases were carcinomas arising in microglandular adenosis, one of which contained areas of acinic carcinoma-like features. The other case was a mammary carcinoma with prominent microglandular adenosis and also acinic cell carcinoma growth patterns. In the latter case, the patient had a history of neoadjuvant chemotherapy; and cells with coarse granules were found in both the pretreatment and posttreatment specimens. Although all 3 tumors were negative for HER2/neu, 2 tumors were estrogen receptor/progesterone receptor negative and one was estrogen receptor/progesterone receptor positive. Follow-up for 2 patients at 12 months and 3 years showed no evidence of disease, and the other patient died of her disease at 34 months. We provide a review of the literature and conclude that prominent coarse eosinophilic granules are a rare and nonspecific feature in breast epithelium. The clinical significance remains to be investigated, given the limited experience.