Expression of KIT (CD117) in renal cell carcinoma and renal oncocytoma.
OBJECTIVE
Overexpression of KIT (CD117), a tyrosine kinase receptor, has been reported in a variety of tumors, some of which are susceptible to therapy with imatinib mesylate. Our aim was to analyze KIT expression immunohistochemically in renal cell carcinomas (RCCs) and in oncocytomas.


METHODS
Routinely processed, paraffin-embedded specimens from 61 RCCs and 13 renal oncocytomas were investigated immunohistochemically. Cytoplasmic and membrane-bound KIT staining of tumor cells was determined semiquantitatively. A subset of cases was additionally analyzed for point mutations of c-kit exon 17 by peptide nucleic acid-mediated nested polymerase chain reaction-clamping.


RESULTS
All cases of oncocytomas and chromophobe RCCs showed membrane-bound KIT positivity, while about three-quarters of cases showed cytoplasmic reactivity. All other types of RCC were found KIT negative. Within the group of chromophobe RCCs, negative cytoplasmatic KIT reactivity was significantly correlated with advanced tumor stage (pT > or = 2; p = 0.036). Analysis of c-kit exon 17 revealed no 'gain-of-function' mutation like the codon 816 Asp-->Val mutation (D816V).


CONCLUSIONS
KIT expression is a hallmark of oncocytoma and chromophobe RCC. Since all other types of RCC were found to be KIT negative, immunohistochemical KIT reactivity may be used as an additional diagnostic criterion to distinguish chromophobe RCC from other RCC types. KIT reactivity and the absence of c-kit mutation D816V in chromophobe RCC justify speculations that imatinib mesylate therapy could be effective in patients with advanced disease.
Krüger
Stefan
S
Institute of Pathology, University of Schleswig-Holstein, Campus Lübeck, Lübeck, Germany. krueger@patho.uni-luebeck.de
Sotlar
Karl
K
Kausch
Ingo
I
Horny
Hans-Peter
HP
D018249:Adenoma, Oxyphilic / Q000737:chemistry* / Q000473:pathology; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D002292:Carcinoma, Renal Cell / Q000737:chemistry* / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007680:Kidney Neoplasms / Q000737:chemistry* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis*
D014408:Biomarkers, Tumor; D019009:Proto-Oncogene Proteins c-kit