A distinct expression pattern and point mutation of c-kit in papillary renal cell carcinomas.

KIT is expressed not only in tumors derived from hematopoietic stem cells, melanocytes, germ cells, mast cells, and interstitial cells of Cajal, but also in other malignancies such as chromophobe renal cell carcinoma. This pattern of KIT expression prompted us to investigate the expression and mutation of c-kit gene exons 9, 11, 13, 17, and intron 17 in the different subtypes of renal cell carcinomas (n=66) and non-neoplastic kidneys (n=12). We found that KIT showed strong immunoreactivity in the cytoplasm of papillary renal cell carcinomas (100%), but on the cell membranes of chromophobe renal cell carcinomas (100%). Interestingly, a specific point mutation of the c-kit intron 17 (T->A) was found only in papillary renal cell carcinomas (94%). Our study demonstrates that the expression pattern and one mutation of c-kit may distinguish papillary renal cell carcinomas.