Breast carcinoma with osteoclast-like giant cells: immunohistochemical and ultrastructural study of a case and review of the literature.

We describe an unusual case of infiltrating ductal carcinoma, not otherwise specified, containing numerous benign stromal osteoclast giant cells (OGCs). Macroscopically, the tumor appeared as a well-outlined dark brown mass and was initially interpreted as a benign lesion on the mammograms. OGCs were uniformly distributed in the tumor and were found in vascularized, hemorrhagic stroma often abutted on the nests of tumor cells. Electron microscopy supported a histiocytic origin of the OGCs, but immunohistochemistry failed to confirm the observation. The patient was alive and well 30 months following the operation. A review of the literature concerning breast carcinoma with OGCs is also presented.