Metastatic renal cell carcinoma to the oral cavity and clear cell mucoepidermoid carcinoma: comparative clinicopathologic and immunohistochemical study

Background. Metastatic clear cell renal cell carcinoma (CCRCC) should be considered in differential diagnosis of intraoral clear cell tumors, including mucoepidermoid carcinoma (MEC). Objective and study design. We compared the clinical, histologic, histochemical, and immunohistochemical characteristics of 9 oral metastatic CCRCCs and 8 intraoral clear cell MECs. Results. Oral metastatic CCRCC affected salivary-gland containing tissues in 7 cases (78%). Microscopically, oral metastasis revealed a proliferation of neoplastic clear cells arranged in an alveolar pattern with central blood vessels, features that were not seen in any intraoral clear cell MEC. Mucicarmine staining was positive only in clear cell MEC. Immunohistochemistry showed similarities in cytokeratin expression; vimentin and CD10 were expressed in all oral metastatic CCRCCs but in only 1 clear cell MEC each. Conclusions. Besides clinical history, the alveolar pattern, vessel distribution, absence of mucicarmine staining, and vimentin and CD10 immunoexpression are useful in histologic differential diagnosis of CCRCC and clear cell MEC. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 109: e22-e27)