Malignant mixed tumors of salivary gland origin.

Abstract

One hundred and thirty-four salivary gland tumors originally diagnosed as malignant mixed tumor at the Armed Forces Institute of Pathology and the Medical College of South Carolina were analyzed. These were reclassified and only 25 were found to possess specific histopathologic criteria necessary for the diagnosis of malignant mixed tumor. Where possible, the clinical behavior, therapy, and prognosis were correlated with the histopathology. The malignant mixed tumor was found primarily in the parotid gland and was observed more frequently in men. The median age of patients with this tumor was 38 years (60% occurred prior to age 40). Pain and fixation of the tumor could not be correlated with malignancy. Sixty-four percent of these tumors presented as primary malignant mixed tumors. Histologically proven metastases were observed in 71% of the cases, with lung, lymph node, central nervous system, and bone the most frequent sites. Certain histopathologic features of the malignant mixed tumor can be correlated with eventual metastases. Although the pathogenesis of the malignant mixed tumor remains undetermined, the results of this study indicate that this neoplasm is malignant from the onset and does not develop from malignant transformation of a preexisting “benign” mixed tumor.