Primary basaloid carcinoma of the nipple with associated squamous cell carcinoma in situ.

Basaloid carcinomas have been documented in various anatomic locations. We describe a primary invasive adenocarcinoma of the nipple with extensive basaloid features that was also associated with squamous cell carcinoma (SCC) in situ and an aggressive behavior. A 69-year-old woman without a history of breast neoplasia presented with right nipple pain. Biopsy of the nipple revealed SCC in situ. One year later, she returned with nipple ulceration. An excisional specimen showed a 1.7 cm nodule composed of invasive sheets and ribbons of basaloid cells with numerous mitoses, extensive tumor necrosis and evidence of glandular differentiation. SCC in situ was present in the overlying epidermis. The differential diagnosis included a primary basaloid adenocarcinoma of the nipple, basal cell carcinoma of the nipple, neuroendocrine carcinoma, melanoma, basaloid variant of adenoid cystic carcinoma and metastatic disease. Immunohistochemical profile of this tumor supported a primary basaloid adenocarcinoma of the nipple. Although the initial sentinel lymph node biopsy was negative, within a year of diagnosis, the patient developed ipsilateral axillary node and pulmonary metastases. To the best of our knowledge, this is the first case of basaloid carcinoma to be documented in this anatomic site.