Immunohistochemistry of RCC tumors demonstrated that in the majority of tumors staining for complement was found in infiltrating immune, endothelial, and stromal cells whereas tumor cells did not show positive staining (80) These data are consistent with functions of complement in the regulation of the immunosuppressive microenvironment However, there is a portion of high-grade tumors that exhibited strong cytoplasmic staining for C3. The gene discussed is C3; the disease is renal cell carcinoma.