Kidney-specific cadherin, a specific marker for the distal portion of the nephron and related renal neoplasms

Renal cell neoplasms are presumably derived from different cell types of the nephron. Clear cell and papillary renal cell carcinoma (RCC) are thought to be of proximal tubular origin, whereas oncocytoma and chromophobe RCC are derived from intercalated cells of distal nephron. A few molecules, such as RCC marker and CD10, have been shown to be markers for clear cell RCC and papillary RCC. Such markers are not yet available for renal tumors presumably of the distal nephron. The expression of kidney-specific (Ksp) cadherin, a recently cloned gene thought to be transcribed exclusively in the kidney, was studied in normal human kidney, as well as in 105 primary renal neoplasms, including 42 clear cell RCC, 30 papillary RCC, 13 chromophobe RCC, and 20 oncocytomas. The expression patterns were compared with those of RCC marker. The Ksp-cadherin expression was noted preferentially in distal convoluted tubules with a basolateral membrane stain in normal kidney. All 13 chromophobe RCC and 19 of 20 oncocytomas showed diffuse and strong immunoreactivity for Ksp-cadherin, while only 14% clear cell RCC and 13% papillary RCC showed focal positivity. The RCC marker expression was detected in 85%, 98%, 15% and 0% of clear cell RCC, papillary RCC, chromophobe RCC, and oncocytoma, respectively. A few clear cell RCC and papillary RCC showed dual expression of both RCC marker and Ksp-cadherin, which appear to have distinct histologic features. These results demonstrated high sensitivity and specificity of Ksp-cadherin for distal convoluted tubules, which can be used as adjunct for diagnosis of chromophobe RCC.