Prognostic factors in malignant mixed tumors of the salivary gland: correlation of immunohistochemical markers with histologic classification.

Malignant mixed tumor of salivary glands is a rare tumor whose variable behavior and prognosis are related for the most part to the clinical stage and histologic grade of the carcinomatous component. The purpose of this study is to predict prognosis by comparing the histologic grading and subclassification of the carcinomatous component with the immunohistochemical reactivity for E-cadherin, P53 mutation protein, and cellular proliferation (Ki67). Stains were performed on formalin-fixed paraffin-embedded tissue sections from 18 cases of malignant mixed tumor. Clinical follow-up was obtained for each patient. Regional lymph node and distant organ metastases were the criteria for poor prognosis. Of seven cases with lymph nodes metastasis, five were high-grade tumors (with one subsequent death from brain metastasis) and two were low-grade. Of the eight high-grade tumors, positivity for Ki67, p53, and E-cadherin were noted in six, four, and two cases, respectively. In contrast, of the 10 low-grade tumors, two stained with Ki67, five with p53, and none with E-cadherin. Most notably, all seven metastatic cases (as opposed to only one of 11 nonmetastatic tumors) had Ki67 reactivity of more than 10%. We conclude that malignant mixed tumor represents a spectrum of malignancies in which the clinical behavior is closely related to the carcinomatous element. In addition to histologic grading, Ki67 is a useful prognostic marker in the evaluation of malignant mixed tumor while p53 and E-cadherin appear to be of limited value. Copyright 2002, Elsevier Science (USA). All rights reserved.