Cathepsin H expression distinguishes oncocytomas from renal cell carcinomas

Background Because the differential diagnosis of oncocytoma and renal cell carcinoma lacks specificity: new methods supporting correct diagnostic deci sions are welcome. Material and Methods. Sixteen cases of renal oncocytoma, and 16 sex-, age-, and stage- matched controls of renal cell carcinoma (T1 -2N0M0) Mere studied. The minimum follow up exceeded ten years. There were no deaths due to neoplasm among oncocytomas, but 4 patient died with metast atic disease among cancer patients. Immunohistochemical staining for cathep sin H was quantified by 3 histoscores. The histoscores evaluated: I) even c ytoplasmic staining of neoplastic cells, 2) granular staining, or 3) total staining. Results. 100% distinction was possible with the even cytoplasmic staining score. Total staining distinguished 87.5%, and granular staining 2 5% of neoplasms. CAM 5.2 cytokeratin, or vimentin distinguished 84.4% or 56 .6% of these tumors, respectively. Conclusions. Cathepsin H histoscore on e ven cytoplasmic immunostaining is an excellent method for the distinction o f oncocytomas and renal cell carcinomas.