Fine‐needle aspiration cytology and immunohistology of low‐grade adenosquamous carcinoma of the breast

Low-grade adenosquamous carcinoma of the breast (LASCB) is a relatively recently-described, rare histotype of breast cancer that has a favorable prognosis. Its principal microscopic features are the presence of "syringoid" ("tadpole"-shaped) ductal profiles of tumor cells, a bland and modestly cellular stromal background, and the variable presence of keratinizing ("epidermoid") cell groups. As such, the basic image of LASCB is quite similar to that of microcystic adnexal or adenosquamous carcinoma of the skin or "syringomatous adenoma" of the nipple. We report the fine-needle aspiration cytologic (FNA) attributes of this neoplasm, as well as its immunohistochemical characteristics and differential diagnosis.