Breast, Adenoid cystic carcinoma

Adenoid cystic carcinoma is a relatively rare variant of breast carcinoma that consists of both ductal epithelial and basal myoepithelial cell types. This morphologic entity is important to recognize and accurately diagnose because it has a relatively good prognosis, despite the fact that it is typically negative for ER, PgR, and HER2 biomarkers.

This case demonstrates a classic, cribriform pattern of growth consisting of nests of cells with rigid punched out spaces like in other anatomic locations. However, trabecular and solid variants have been described. Myxoid, basement membrane-like material filling some of the punched-out spaces as seen in this example is also well described in this entity. The key morphologic differential diagnosis of adenoid cystic carcinoma includes collagenous spherulosis and cribriform carcinoma (in-situ or invasive). In conjunction with the triple negative biomarker status, immunohistochemistry (CD117, S100, myoepithelial markers) highlighting the dual cell population can help to distinguish adenoid cystic carcinoma from these other two entities.