Cytodiagnosis of pure primary squamous-cell carcinoma of the breast by fine-needle aspiration cytology.

In this communication five cases of pure primary squamous-cell carcinoma of the breast are presented in which the diagnosis was made by fine-needle aspiration cytology. All patients were women. The aspiration cytodiagnosis was further confirmed by subsequent examination of cell blocks from the aspirated material and biopsy of the breast mass. The cytohistologic features in all cases were characterized by numerous malignant squamous cells with keratinizing cytoplasm, hyperchromatic dense nuclei, coarse chromatin, thickened nuclear membranes, keratin debris, and background necrosis. The identification of malignant squamous cells as predominant cells in aspirate samples from the breast is quite important and should be followed by a search for other sources of a primary tumor before a diagnosis of pure primary squamous-cell carcinoma of the breast is accepted. The value of immunocytochemical study despite immunopositivity for cytokeratin and epithelial membrane antigen (EMA) and immunonegativity for carcinoembryonic antigen (CEA) and B72.3 was considered to be somewhat uncertain.