Renal cell carcinoma with osteoclast-like giant cells.

Primary extraskeletal epithelial neoplasms with osteoclast-like giant cells are rare. We describe a case of renal cell carcinoma with a sarcomatoid component and non-neoplastic osteoclast-like giant cells. The giant cells were noted in both the conventional and the sarcomatoid components of the neoplasm. Immunohistochemical studies indicate that these cells are monocyte/histiocyte in origin and most probably a host stromal reaction to the neoplasm.