Results from this study revealed that: 1) 93% of RCCs lost GRIM-19 expression, and in the remainder only weak expression was noted, (2) Loss of GRIM-19 appears to be a characteristic of clear cell type RCCs and (3) a low frequency loss of GRIM-19 also occurs in prostatic and transition cell carcinomas. This evidence concerns the gene NDUFA13 and transitional cell carcinoma.