Fine-needle aspiration cytology of breast masses in pregnant and lactating women.

Eleven pregnant women with breast masses that arose during pregnancy or in the postpartum period underwent fine-needle aspiration biopsies. Cytologic examination demonstrated a spectrum of morphologic features, including (1) a pattern of dissociated epithelial cells stripped of their cytoplasm along with small clusters of cells having a frayed secretory type of cytoplasm; (2) larger epithelial groups with nuclear pleomorphism, prominent irregular nucleoli, and abundant vacuolated cytoplasm; (3) cellular smears, often with an inflammatory background and proteinaceous debris; and (4) microtissue fragments showing features of lobular hyperplasia. This article illustrates the clinical utility of fine-needle aspiration biopsy in evaluating breast masses in pregnant and lactating women and discusses the potential hazards for a false-positive diagnosis of malignancy in these patients.