Squamous carcinoma of the breast: diagnosis by aspiration cytology.

Squamous carcinoma is a rarely encountered lesion in the breast, and its diagnosis by aspiration cytology is unreported. Six cases of squamous carcinoma occurring in the breast, all diagnosed preoperatively by cytology, are discussed. Cytologic and histopathologic features of both primary and secondary carcinomas, pure and metaplastic types, are described, together with aspects of etiology, morphology and prognosis.