Choriocarcinoma metastatic to the breast diagnosed by fine needle aspiration

Fine needle aspiration (FNA) was used to study nodules in the left breast of a patient with a previous history of uterine choriocarcinoma. The FNA smears contained numerous malignant mononucleated cells and multinucleated giant cells. The cytologic diagnosis was metastatic choriocarcinoma, which was confirmed by histologic study of excised tissue. That diagnosis would have been difficult to make cytologically if the previous history had not been known; the differential diagnosis of multinucleated giant cells in an aspirate from a breast mass is discussed.