A case of renal cell carcinoma unclassified with medullary phenotype without detectable gene deletion

Renal cell carcinoma unclassified with medullary phenotype (RCCU-MP) is a rare variant of renal medullary carcinoma (RMC) characterized by loss of SMARCB1 (INI1 / SNF5 / BAF47) protein expression in patients without sickle cell trait. Here, we report a case of RCCU-MP in a Japanese patient who had experienced colon cancer 13 years ago, gastric cancer 11 years ago and lung cancer 9 years ago and had received hemodialysis for 15 years. This is the first report of RCCU-MP in Japan. The patient was not of African descent, and did not have SCT or any other hereditary blood abnormality typical of RMC. The tumor was located in the left kidney, and was composed histologically of rhabdoid cells with marked lymphocyte infiltration; it was immunohistochemically negative for SMARCB1. We were, however, unable to detect mutation in the SMARCB1 gene, reduced messengerRNA expression, or deletion or translocation of chromosome 22, where the SMARCB1 gene is located. These results suggest that RCCU-MP may not involve the hemizygous loss of this gene noted in typical RMC cases.