Cytodiagnostic patterns of metaplastic breast carcinoma in aspiration samples: a study of 14 cases.

Metaplastic breast carcinomas (MBCs) are not only uncommon neoplasms but also show a myriad of cytomorphologic patterns in aspiration samples. These tumors comprise less than 5% of breast malignancies and have an uncertain prognosis. In this study, the fine-needle aspiration cytologic features of 14 MBCs with the identification of two distinct malignant cell populations are presented, based on which a definitive diagnosis was possible in 12 of the 14 cases. In the remaining 2 cases the diagnosis of MBC was substantiated after study of cell blocks from the aspirate, which were made in all the cases. Furthermore, the diagnosis of MBC was also confirmed subsequently on tissue examination. The various combinations of patterns included malignant ductal, squamous, and sarcomatous (including heterologous) elements and multinucleated osteoclastic giant cells. As a result of this study, it was felt that if malignant breast aspirates on careful examination show two or more distinct neoplastic elements, the diagnosis of MBC may be possible.