Fine Needle Aspiration Cytology of Breast Pure Squamous Cell Carcinoma: Cytologic Differential Diagnosis from Mammary Lesions Associated with Aberrant Squamous Cells

Fine needle aspiration (FNA) cytology of two cases of breast pure squamous cell carcinoma (SCC) and one invasive carcinoma mixed with SCC is reported. Cytopathologic findings of breast cancer vary greatly because mammary carcinomas are composed of many subtypes. Squamous cells, both malignant and benign, are occasionally seen in the breast FNA smears. Many differential diagnoses including various neoplastic and non-neoplastic diseases should be raised when squamous cells are observed in the mammary FNA smears. Squamous cells endowed with severe grade atypia obviously indicate malignancy. However, apparently benignlooking squamous cells are seen in the FNA specimens of both malignant and benign breast disorders. Accurate interpretation of cytologic findings is essential for discriminating malignant diseases from benign conditions. As prognosis and therapeutic options depend on tumour subtypes, deducing tumour histologic subtypes from cytologic specimens is useful for the appropriate treatment planning. FNA samples of pure SCC and invasive carcinoma mixed with SCC were examined in detail in an attempt to clearly define the cytopathologic characteristics of pure breast SCC. Careful review of the FNA slides of these cases helped us to recognize cytomorphologic findings useful in the differential diagnoses and predicting of histologic pictures of mammary disorders containing squamous cells.