Distinguishing
renal oncocytoma from chromophobe and other
renal carcinomas is essential, considering their differing
biological potentials. Although
renal oncocytoma is considered a benign
tumor,
chromophobe renal cell carcinoma has potentially malignant
biological behavior. The numerous reported studies on distinguishing these 2 entities have been based on morphological, histochemical, immunohistochemical, ultrastructural, and cytogenetic features. But none of these features has proven to be reliably specific, especially in
tumors with overlapping phenotypes. We report a novel immunohistochemical approach based on the expression of a recently described kidney-specific
cadherin (Ksp-
cadherin) for the differential diagnosis of these 2
tumors. We compared Ksp-
cadherin expression in 212 renal
tumors, including 102 clear cell
renal carcinomas, 46 papillary
renal cell carcinomas, 30 chromophobe
carcinomas, 3
collecting duct carcinomas, and 31 oncocytomas. In addition, we examined the expression of
epithelial membrane antigen,
vimentin, CK7, and Hale's colloidal
iron staining. We found that chromophobe
renal cell carcinomas consistently (96.7% of cases) demonstrated a distinctive membrane pattern of Ksp-
cadherin expression, whereas renal oncocytomas (3.2%), clear cell
renal cell carcinomas (0%), papillary
renal cell carcinomas (2.2%), and
collecting duct carcinomas (0%) usually did not express Ksp-
cadherin. CK7 expression was found in 90.0%, 6.5%, 7.8%, 76.1%, and 33.3% of these
tumor cases, respectively. Whereas CK7 was detected in different types of
renal cell carcinomas, Ksp-
cadherin was expressed almost exclusively in chromophobe
renal cell carcinomas. Immunohistochemical analysis of Ksp-
cadherin offers a fast, reliable approach for the distinguishing between
renal oncocytoma and
chromophobe renal cell carcinoma that is applicable for routine pathology laboratory studies without the need for time-consuming and costly ancillary studies.