Immunohistochemical study of c-KIT (CD117) expression in renal cell carcinoma

Certain subtypes of Renal cell carcinomas (RCCs) are diagnostically challenging owing to their overlapping histopathological features. Recently, c-KIT (CD117) has come into focus as a potential diagnostic marker of some renal tumors. c-KIT also provides a potentially suitable for targeted tumor therapy. The present study was designed to investigate the expression of c-KIT in RCCs in order to evaluate its diagnostic usefulness as a phenotypic marker and to establish the basis for a new possible therapeutic modality.

The present work was conducted on 49 patients with RCC: Clear cell RCC (CRCC): 30 cases (61.22%); chromophobe RCC (ChRCC): 9 cases (18.37%); papillary RCC (PRCC), type I: 5 cases (10.20%); and carcinoma of the collecting ducts of Bellini (CdRCC): 5 cases (10.20%). The expression of c-KIT was assessed using immunohistochemistry. The diagnostic performance of c-KIT expression was evaluated using ROC curve analysis.

Overall, 11 (22.5%) cases of RCC showed c-KIT expression: 2 (6.7%) CRCC, 7 (77.8%) ChRCC, and 2 (40.0%) CdRCC. Among the study group, ChRCC had the highest frequency (p=.001) and staining score (p=.001) for c-KIT. In addition, only ChRCC showed membranous pattern of c-KIT staining, while other tumors showed cytoplasmic staining (p=.013). c-KIT showed a sensitivity of 77.78%and a specificity of 95%for the diagnosis of ChRCC. The relation between c-KIT expression and clinicopathological parameters was not significant. High grade tumors had a statistically significant higher total score of c-KIT expression (p=.023).

c-KIT is frequently and significantly expressed in chromophobe RCC suggesting that it might play a role in its pathogenesis. Immunohistochemical detection of c-KIT expression could be used to aid histological diagnosis of chromophobe RCC with a high sensitivity and specificity. The substantial c-Kit immunoreactivity in chromophobe RCC may be of clinical importance especially in the field of targeted therapy.