True malignant mixed tumor (carcinosarcoma) of parotid gland with unusual mesenchymal component: a case report and review of the literature

True malignant mixed tumor (carcinosarcoma) of the salivary gland is an extremely rare tumor. By definition, it is composed of both malignant epithelial and malignant mesenchymal elements. The most common type of the former is squamous cell carcinoma or adenocarcinoma and the most common type of the latter is chondrosarcoma, followed in frequency by fibrosarcoma, leiomyosarcoma, osteosarcoma, and in rare instances liposarcoma. We report a case of true malignant mixed tumor of the parotid gland in association with a pleomorphic adenoma in a 47-year-old man that contained a very unusual type of malignant mesenchymal component, rhabdomyosarcoma. Cytologic and histologic features and immunohistochemical results are presented. In addition, the literature is reviewed, and the possible histogenesis and pathogenesis of malignant mixed tumor of the salivary gland are briefly discussed.