IMMUNOHISTOCHEMICAL EXPRESSION OF METABOLIC MARKERS IN PLEOMORPHIC ADENOMA AND CARCINOMA EX PLEOMORPHIC ADENOMA

Objective: To perform a comparative study focusing on the morphologic and immunohistochemical features of pleomorphic adenomas (PAs) and carcinoma ex pleomorphic adenomas (CXPAs) of the minor salivary glands. Study design: Forty PAs and 10 CXPAs were retrieved from the archives of 3 pathology laboratories, and the diagnoses were reviewed and confirmed. Immunohistochemical reactions were done for p53, Ki67, mammaglobin, and the metabolic markers of glucose transporter 1 (GLUT-1) and adipophilin. Results: The most common subtypes of CXPA were ductal carcinoma (n = 4), clear cell carcinoma (n = 3), and myoepithelial carcinoma (n = 2). The morphologic features suggestive of malignancy were the presence of mitosis, cellular pleomorphism, and extracapsular component. Compared to PA, CXPA demonstrated a higher number of Ki67- and p53-positive cells, in addition to higher expression of GLUT-1 and adipophilin. Mammaglobin expression was observed in the malignant areas, mainly in the ductal CXPA, being negative in the benign reminiscent PA. Conclusion: The diagnosis of CXPA based only on the morphologic aspects can be difficult; thus, an association of the morphologic and immunohistochemical features, particularly high number of Ki67- and p53-positive cells, is essential for a proper diagnosis. Other metabolic markers such as GLUT-1 and adipophilin may be also helpful, although their exact utility remains to be determined.