Carcinoma of the parotid gland with osteoclastlike giant cells. Immunohistochemical and ultrastructural observations.

We describe an unusual type of carcinoma of the parotid gland in a 67-year-old man. Because of rapid tumor growth, radical parotidectomy was done. Light microscopic study of the tumor revealed focal gland formation with transition to anaplastic carcinoma. Among the undifferentiated mononuclear cells and bizarre large cells were scattered many osteoclastlike multinucleated giant cells. Immunohistochemical studies on paraffin sections revealed positive staining for epithelial membrane antigen in the epithelial component; however, the multinucleated giant cells were clearly negative for this antigen. Reactions for other cell constituents (carcinoembryonic antigen, alpha 1-antitrypsin, alpha-1-antichymotrypsin, Leu-M1, Leu-M3, lysozyme, and factor VIII-related antigen) were negative in both epithelial and giant cell components of the tumor. Electron microscopy revealed poorly formed cell junctions and numerous microvilli on the surface of the mononuclear tumor cells and multinucleated giant cells, features considered not of diagnostic significance. Similar to carcinomas with osteoclastlike multinucleated giant cells in other organs, this parotid gland tumor has shown clinical and morphologic evidence of aggressive growth; pulmonary metastases developed and the patient died 28 months after radical surgery.