Primary pure squamous cell carcinoma of the breast.

Primary squamous cell carcinoma (SCC) of the breast is an extremely rare tumor. It is diagnosed when the malignant cells are entirely of squamous type, the tumor is independent from overlying skin, and other primary SCC sites are excluded. This report presents clinical, radiologic, and histologic correlative findings of a patient diagnosed with pure SCC of the breast. Literature review suggests that primary SCC tumors of the breast are large, often cystic lesions, with a low rate of nodal involvement, no expression of estrogen and progesterone receptors, and resistance to the chemotherapy regimens commonly used in breast cancer.