Carcinosarcoma of the parotid gland: report of a case with cytohistologic and immunohistochemical findings.

True malignant mixed tumors (carcinosarcomas) of salivary gland origin are exceedingly rare and demonstrate malignant epithelial and stromal components. We report a case of parotid gland carcinosarcoma that showed squamous cell carcinoma and malignant fibrous hystiocytoma without clinical or histologic evidence of a preexisting pleomorphic adenoma. This tumor consisted of 2 histologically different populations of cells without evidence of a common origin from the myoepithelial cell, which is the putative precursor cell of pleomorphic adenoma and its derived carcinosarcoma. In addition to supplementing the literature, this case report includes cytohistologic and immunohistochemical analyses that provide further insights into the variable histogenesis of this neoplasm and the distinction between de novo carcinosarcoma and carcinosarcoma originating from pleomorphic adenoma.