Immunocytochemical and ultrastructural study of the rare osteoclast-type carcinoma of the breast in a fine needle aspirate.

The cytologic findings in a fine needle aspirate from a case of the rare osteoclastlike carcinoma of the breast are described along with the immunocytochemical and ultrastructural findings. The ultrastructural and immunocytochemical findings suggest that the osteoclastlike giant cells in this type of carcinoma are not of epithelial origin, but rather are reactive and of a histiocytic-stromal origin.