Fine needle aspiration cytology of sclerosing adenosis of the breast.

OBJECTIVE To analyze the cytologic findings of sclerosing adenosis of the breast. STUDY DESIGN We reviewed the fine needle aspiration (FNA) cytologic slides of 7 cases of sclerosing adenosis of the breast and compared the cytologic findings with those of 10 cases of fibroadenoma and 7 cases of fibrocystic change. RESULTS The smears of sclerosing adenosis were moderately to markedly cellular, consisting of small to large groups of benign epithelial cells arranged with variable architecture. Acinar sheets, scattered individual epithelial cells and small, dense, hyalinized stroma were found in all cases of sclerosing adenosis. Epithelial cells in sclerosing adenosis appeared more frequently as acinar sheets and discohesive individual cells than did those of fibroadenoma (P < .05). However, the branching pattern of epithelial sheets, large sheets and bipolar, naked nuclei were commonly found in fibroadenoma (P < .05). Fibroadenoma had large, hypocellular, fibromyxoid stroma, whereas sclerosing adenosis had small, dense, hyalinized stroma occasionally attached to the epithelial sheets. As compared with fibrocystic change, sclerosing adenosis had similar findings but showed more abundant cellularity, acinar sheets and individual epithelial cells, and the presence of stroma (P < .05). CONCLUSION Findings of frequent acinar sheets and small, dense, hyalinized stroma attached to epithelial sheets can aid the FNA cytologic diagnosis of sclerosing adenosis. Awareness of the presence of scattered individual epithelial cells in cytologic smears of sclerosing adenosis can help prevent a misdiagnosis of malignancy.