Carcinoma ex pleomorphic adenoma: pathologic analysis of 73 cases

Pathologic factors of predictive value for carcinoma ex pleomorphic adenoma (CXPA), an aggressive salivary gland malignancy, are poorly defined. Because residual mixed tumor may be relatively inconspicuous and various carcinoma subtypes are encountered, misdiagnosis is common. To describe the pathologic features and identify potential prognostic factors, we retrospectively examined 73 cases of CXPA of the major salivary glands treated at Mayo Clinic. Paraffin section immunostaining for keratins (AE1/AE3, CK7, CK20), epithelial membrane antigen, carcinoembryonic antigen, vimentin, actin, S-100 protein, glial fibrillary acidic protein, and p53 and c-erbB-2 oncoproteins was performed in 69 cases. DNA content and proliferation indices were determined by digital image analysis of Feulgen- and MIB-I-stained sections, retrospectively. Survival was calculated by the Kaplan-Meier method, and prognostic variables were analyzed with the log-rank test. The carcinoma component was predominant in 82% of tumors. Adenocarcinoma not otherwise specified (31 cases) and salivary duct carcinoma (24 cases) were the most frequent histologic subtypes. Sixty-two tumors were high grade (Broders 3 or 4). Residual mixed tumor was extensively hyalinized in 54 cases. Pathologic features significantly associated with overall survival included pathologic stage (P =.009), tumor size (P =.012), grade (P =.005), proportion of carcinoma (P =.004), extent of invasion (P =.002), and proliferation index of carcinoma (P =.03). Of 4 patients with intracapsular (noninvasive) carcinoma, none had an adverse outcome. The immunohistochemical profile of CXPA included positive staining reactions in the malignant component for AE1/AE3 in 97% of cases, CK7 in 94%, epithelial membrane antigen in 86%, carcinoembryonic antigen in 75%, vimentin in 52%, and S-100 protein in 29%. Expression of p53 and c-erbB-2 oncoproteins was detected in 41% and 30% of the carcinomas, respectively, but neither was associated with decreased survival. High-grade salivary adenocarcinoma that is difficult to classify should raise the suspicion of possible CXPA. Intracapsular carcinoma has a benign clinical course. Significant prognostic factors in CXPA include tumor stage, grade, proportion of carcinoma, extent of invasion, and proliferation index.