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Abstract
The underlying molecular mechanisms of renal cell carcinoma (RCC) are poorly understood and more reliable markers are needed for its early diagnosis. CD70 is a type II transmembrane protein that was found to be overexpressed in RCC. Normally, CD70 is not expressed in renal parenchyma. Thirty four paraffin embedded biopsies were collected including; 8 clear cell RCC, 7 papillary RCC, 3 chromophobe RCC, 5 clear cell RCC with sarcomatoid change; all with their adjacent normal renal parenchyma, 4 oncocytoma, 2 cystic nephroma and finally 5 randomly selected normal renal biopsies. All were examined immunohistochemically for CD70 protein expression. CD70 was expressed in 9 cases out of 13 of the clear cell variant and was expressed in less than 5% of malignant cells in only one case in each of the papillary and sarcomatoid variants. No expression was detected in chromophobe RCC, oncocytoma, cystic nephroma or in the normal renal tissue. No association was found between CD70 expression and stage or nuclear grade of RCC. CD70 is a gene that is specifically overexpressed in the clear cell variant of RCC. It is not expressed in normal renal parenchyma or in benign renal neoplasms