Apoptotic markers (P53, Bcl-2 and Bax) expression in renal oncocytoma and chromophobe renal cell carcinoma

Background and Purpose: Renal oncocytoma (RO) and eosinophilic variant of chromophobe renal cell carcinoma (ChRCC) have overlapping morphologic, immunohistochemical, histochemical and ultrastructural features. Their distinction is mandatory since RO is a benign tumor, while ChRCC is a low-grade malignant tumor which has metastatic potential and may undergo sarcomatoid transformation. The aim of this study was to determine expression of P53, Bcl-2 and Bax in ROs and ChRCCs and to explore whether these markers could be useful in differential diagnosis of RO and ChRCC. Patients and Methods: We analyzed 61 cases (28 ChRCCs and 33 ROs) by immunohistochemistry using primary antibodies to P53, Bcl-2 and Bax. The staining percentage and staining intensity scores were multiplied to give immunohistochemical staining index (ISI). Results and Conclusion: All specimens showed positive reaction for Bcl-2 and Bax. There was no significant difference in the ISI for Bcl-2 and P53. Statistical analysis showed significant difference in the ISI of Bax between ROs and ChRCCs. Moreover, cases of ROS had cytoplasmic pattern of reaction for Bax, while the pattern of reaction for Bax in cases of ChRCCs was membranous. Further studies are needed to confirm the possible use of Bax immunostaining in differential diagnosis of RO and ChRCC.