Immunohistochemical distribution of vitamin B12 R-binder in renal cell carcinoma.

Renal cell carcinomas and normal kidney tissues were examined for the expression of vitamin B12 R-binder by the indirect immunoperoxidase method. In normal kidney tissue, the presence of the vitamin B12 R-binder was shown to be confined to the straight portion (pars recta) of proximal tubules. Seven of the 38 cases of renal cell carcinoma (18%) expressed the vitamin B12 R-binder antigen. This provides a further evidence of the proximal tubular nature of renal cell carcinoma, and suggests that a small proportion of renal cell carcinomas originate from the straight portion of the renal proximal tubules.