Fine-needle aspiration of fibroadenomas of the breast with atypia: a spectrum including cases that cytologically mimic carcinoma.

We herein report the cytologic and histologic findings in 11 cases of cytologically atypical fibroadenoma (FA). These ranged from cases recognizable as FA but showing epithelial atypia to cases that, even on review, completely mimicked the needle aspiration picture of ductal breast carcinoma. A retrospective review of 45 cases of previously excised FA showed that focal atypia is common (27%). Possible physiologic explanations for atypia in FA, along with strategies for avoiding false diagnoses of malignancy in aspiration smears, are discussed.