Carcinoma in Pleomorphic Adenomas of Salivary Glands

Abstract

Because of the variability of the histological appearance of a given mixed tumor of the salivary gland and because of “recurrences” following less than total removal, biologically benign (not capable of metastasis) mixed tumors have been considered malignant. The true malignant mixed tumor, or more commonly carcinoma, arising from preexisting mixed tumors are unusual and ill-defined in the literature. These tumors make up no more than 5% of the mixed tumor category and occur primarily in the parotid gland. In this report, we present a clinico-pathological appraisal of the malignant mixed tumor based on five cases from the University of Michigan Medical Center and relate our experience to that in the literature. The importance of recognizing the malignant mixed tumor, or “carcinoma ex-mixed tumor,” lies in the accelerated recurrence rate and surprisingly high metastatic rate manifested by this lesion. Minimal treatment is radical total excision. Wide, early excision of the primary “benign” stage of these mixed tumors should reduce the problem of ultimate “malignification.”