Primary squamous cell carcinoma of the breast is a very rare and aggressive malignancy, and very few have been reported in the literature. Here we report a case of an acantholytic variant of a squamous cell carcinoma of the breast in a 60-year-old woman who presented with a lump in the right breast. Histogenesis is controversial as to whether a pure form of squamous cell carcinoma exists or if these malignancies represent an extreme squamous metaplasia within an adenocarcinoma. Prognosis and management is uncertain due to its rarity and controversy over its definition.