The main diagnostic feature of apocrine carcinoma is the cytologic appearance of tumor cells. Architecturally, apocrine ductal carcinoma-in-situ (DCIS) is similar to non-apocrine DCIS and can display comedo, micropapillary (shown here), cribriform, solid, and papillary patterns. In this case, the tumor cells have abundant densely eosinophilic cytoplasm, enlarged nuclei, and one or more punctate nucleoli. The nuclear grade is intermediate. Apocrine snouts can be seen on the luminal aspect of many tumor cells.