Immunophenotypic comparison of salivary gland oncocytoma and metastatic renal cell carcinoma

OBJECTIVES/HYPOTHESIS: The differential diagnosis of oncocytic neoplasms of salivary glands includes both primary and metastatic tumors, one of which is renal cell carcinoma. This study compared immunohistochemical staining characteristics of oncocytomas arising from salivary gland to metastatic renal cell carcinoma using a panel of markers. STUDY DESIGN: Immunohistochemistry for cytokeratin 7 (CK7), cytokeratin 20 (CK20), epithelial membrane antigen (EMA), vimentin, CD10, and renal cell carcinoma marker (RCC) was performed on 10 oncocytomas and compared with ten metastatic renal cell carcinomas. RESULTS: There were overlapping histologic findings in the oncocytomas and metastatic renal cell carcinomas, with oncocytomas displaying clear cell changes in 2 of 10 cases. CK7 was positive in 9 of 10 oncocytomas and CK20 in 8 of 10 (7/10 stained for both), and vimentin was only weakly positive in 4 of 10 oncocytomas. All oncocytomas were EMA positive, with membranous staining, and all were negative for CD10 and RCC. Metastatic renal cell carcinoma was strongly positive for vimentin, EMA, and CD10 in most cases. RCC and CK7 were variably positive in metastatic renal cell carcinomas (4/10), and only 1 of 10 showed weak staining with CK20. CONCLUSIONS: Salivary gland oncocytomas and metastatic renal cell carcinomas share some similar histologic and immunohistochemical characteristics. CD10 and CK20 were the most useful markers to distinguish metastatic renal cell carcinoma from oncocytomas in the salivary gland, whereas RCC, EMA, CK7, and vimentin are not as useful.