PATHOLOGICAL DIFFERENTIAL DIAG-NOSTIC OF CHROMOPHOBE RENAL CELL CARCINOMA AND RENAL ONCO-CYTOMA: LITERATURE REVIEW AND CASE REPORTS

Chromophobe renal cell carcinoma (ChRCC) and renal oncocytoma (RO) are rare tumors that share common histogenesis and similar histological appearance, but possess different clinical course and therapeutic approach. Their differential diagnostics is based on the results of an immunohistochemical study. We offer the use of markers CD117 c-kit (Polyclonal), CD10 (56C6), Vimentin (Vim3), CK7 (OV-TL 12/30). CD117 (KIT) is a tyrosine kinase type III receptor. Now we know that 70-91% ChRCC are CD117 positive. CD10 is a zinc-dependent metal protease. 89-94% of cellular and papillary renal cell carcinomas have a positive reaction to CD10. ChRCCs are usually negative, but 30% of them stain positively with CD10. CK7 (cytokeratin-7) is a protein ex-pressed in a single-layer epithelium that covers internal organs' cavities, glands ducts and blood vessels. The reaction to CK7 in ChRCC is usually diffuse or negative and focal in RO. Vimentin is an intermediate filament of mesenchymal cells. ChRCC gives a negative reaction to vimentin, while RO are focally positive. ChRCCs represent approximately 5% of all renal cell carcinomas. The eosinophilic variant of ChRCC often causes diagnostic difficulties. In the immunohistochemical study, the ChRCC demonstrates negative reaction to vimentin, CD10, RCC and positive reaction to pan-cytokeratin AE1 / AE3, CK7, EMA, CD117, Ksp-Kadherin. RO is a benign neoplasm of the kidney. RO is posi-tive to pancytoceratin AE1 / AE3 and low molecular weight cytokeratin CAM5 and usually negative to vimentin. About two thirds of RO express CD117, but sometimes this phe-nomenon is also actual in ChRCC, as well as the expression of the Ksp-cadherin. In our study, we used the surgical specimens of 23 patients. In 20 cases, the kidney tumors were diagnosed as clear cell renal cell carcinomas. There was a diffuse expression of CD10 (56C6), Vimentin (Vim3). In addition, in 13 cases there was a focal positive reaction to CK7 (OV-TL 12/30). In three cases, we had suspicion of RO or ChRCC. In the case of a 55-year old patient, a positive reac-tion to CD117 c-kit (Polyclonal) and a negative reaction to CD10 (56C6), Vimentin (Vim3), CK7 (OV-TL 12/30) was observed. This tumor was diagnosed as RO. In the case of a 81-year old patient, tumor cells demonstrated negative reaction to Vimentin (Vim3) and CD10 (56C6), positive to CK7 (OV-TL 12/30), focally weak positive to CD117 c-kit (Polyclonal). Basing on the data above, the diagnosis of ChRCC was made. In the case of a 72-year-old patient, tumor cells were negative to Vimentin (Vim3), CD10 (56C6), CD117c-kit (Polyclonal) and positive to CK7 (OV-TL 12/30). Thus, we received controversial data using the di-agnostic panel we selected to verify the diagnosis. The diag-nostic panel including CD117 c-kit (Polyclonal), CD10 (56C6), Vimentin (Vim3), CK7 (OV-TL 12/30) was appro-priate for the differential diagnosis of RO and ChRCC in three described clinical cases, but requires more extensive testing to provide statistically significant results.