Renal medullary carcinoma: molecular, immunohistochemistry, and morphologic correlation

Renal medullary carcinoma, a highly aggressive tumor mainly occurring in patients with sickle cell hemoglobinopathy, is characterized by advanced stage at the time of presentation and poor response to treatment. Currently, the pathogenesis of this tumor is not well understood. In this study, the clinicopathologic features and molecular changes of 15 renal medullary carcinoma cases were evaluated. These cases demonstrated male predominance (M:F=2:1) with a median age of 26 years. The tumors occurred predominantly in the right kidney with an average size of 5.9 cm. Immunohistochemistry analysis showed that the neoplastic cells were positive for CEA (7/8), AE1/3 (8/8), CAM5.2 (7/7), CK7 (5/5), CK20 (4/6), and vimentin (6/6). Absence of SMARCB1 protein expression in tumor cells was demonstrated in all of the 7 cases analyzed. By polymerase chain reaction-based microsatellite analysis, loss of heterozygosity of SMARCB1 was identified in 9 of 10 cases. These data suggest that inactivation of SMARCB1 may play a role in the pathogenesis of renal medullary carcinoma.