Masquerades of malignancy: a review of 4,241 aspirates from the breast.

A total of 4,241 aspirates from the breast were obtained by fine needle aspiration biopsy. Of the 3,809 benign lesions, 61 (1.6%) were interpreted as possibly malignant. In all, excisional biopsy, not mastectomy, was recommended as the next procedure. More than 50% of these misdiagnoses were from aspirates of fibrocystic disease, 15% were from fibroadenomas, and the remainder were from gynecomastia, solitary papillomas, periareolar hyperplasia, pregnancy hyperplasia and granulation tissue. Most errors were based on specimens that were insufficiently cellular or whose poorly preserved cells lacked the majority of the criteria of malignancy.