Fine needle aspiration cytology of phyllodes tumor. Potential diagnostic pitfalls.

We reviewed the fine needle aspiration cytologic findings in six cases of phyllodes tumor (PT). The average age of the patients at the time of the diagnosis was 47 years. Two cases were correctly diagnosed cytologically; both were malignant histologically. Of the histologically benign tumors, two were misdiagnosed as carcinoma, and a third was considered suspicious for carcinoma. The remaining case was diagnosed descriptively as "benign duct epithelium." Possible reasons for overdiagnosis include high cellularity of the smears, the presence of atypical ductal hyperplasia, paucity of the stromal component in the aspirates and occasional dissociation of epithelial cells. Recommendations are offered to prevent misdiagnosis. The cytologic differential diagnosis between fibroadenoma and PT is discussed briefly, and the considerable cytologic overlap that can occur is emphasized. The specific cytologic diagnosis of PT is not possible in many cases, but the presence of certain cytologic features in the correct clinical setting allows the diagnosis to be suggested.