FINAL DIAGNOSIS: RECURRENT TRUE MALIGNANT MIXED TUMOR OF THE RIGHT PAROTID GLAND.
Comment: the recurrent tumor appears to be composed mostly if not exclusively of chondrosarcoma.
Three categories of malignant mixed tumors of salivary glands are described. The most common category is carcinoma ex pleomorphic adenoma ( carcinoma arising from a pleomorphic adenoma. ). It is usually a poorly differentiated carcinoma. Another type is the true malignant mixed tumor, a carcinosarcoma in which both the epithelial and stromal components are malignant. Rarest of all is the so-called benign metastasizing mixed tumor (1).
In most tumors epithelial and mesenchymal components are mixed with each other but in other cases, as seen in this tumor, carcinoma and sarcoma elements occur adjacent to one another. The sarcoma component is most often manifested as chondrosarcoma, as in the present case, but osteosarcoma, fibrosarcoma, myxosarcoma, malignant fibrous histiocytoma and even liposarcoma have been described (2). The epithial element is most often a ductal carcinoma (5), but squamous cell carcinoma was also reported (7)
Grossly these neoplasms are usually unencapsulated and infiltrative. Primary neoplasms range from 2 to 13 cm in greatest dimension. Recurrent tumors as large as 8 cm. have been described (3). The cut surface is usually gray but often contains areas of necrosis, hemorrhage and calcification.
In the major salivary gland the differential diagnosis includes benign mixed tumor and primary and metastatic sarcomas. In the intraoral minor salivary gland spindle cell carcinoma is also a consideration (4).
Carcinosarcoma is an aggressive, high-grade neoplasm and aggressive therapy, including radical surgery, with and without radiation therapy and chemotherapy, is used. Recurrent disease, often multiple episodes, develops in approximately two thirds of patients and metastasis in about half (6). Lung is described as the most common site of metastasis. There is a good corelation between stage and local extension of the tumor and prognosis. Facial nerve palsy and grade of malignancy are important prognostic factors (8).
Contributed by Anna Mnuskin MD, Sheldon Bastacky, MD and Rajiv Dhir, MD