Correlation of c-myc expression with nuclear pleomorphism in human renal cell carcinoma

The expression of the c-myc gene product in renal cell carcinomas was examined by immunostaining with monoclonal antibody (mAb) MYC-1. The effects of preservation and fixation of tissues on staining were first examined. In cryostat sections fixed with 4% buffered formalin for 15 min, staining was observed in the nucleus. On the other hand, in paraffin sections after fixation with 10% formalin, staining was observed in the cytoplasm, but not in the nucleus. Because c-myc protein has been shown to be a nuclear protein, the finding that c-myc protein was not detectable in the nucleus appeared to be due to the preservation or fixation procedures used. Therefore, cryostat sections fixed with 4% formalin were used to investigate the correlation between the reaction of MYC-1 mAb and nuclear pleomorphism in primary and metastatic renal cell carcinomas. Among 41 primary tumors, positive staining was observed in 2 of 17 tumors (12%) of grade 1, 17 of 21 (81%) of grade 2, and all 3 (100%) of grade 3. Among 17 metastatic tumors, positive staining was not observed in any of the 5 (0%) of grade 1 but was observed in 2 of 4 (50%) of grade 2 and all 8 (100%) of grade 3. Thus, the frequency of the positive reaction with MYC-1 mAb was correlated with nuclear pleomorphism in primary and metastatic renal cell carcinomas. The reaction of Ki-67 mAb, which recognized a nuclear antigen present in proliferating cells, was also correlated with nuclear pleomorphism. These findings suggest that the c-myc gene product plays a role in cell proliferation in renal cell carcinomas.