Hale's colloidal iron as a histological stain has been utilized in the past but it is technically challenging to perform and not widely available. As such, many investigators have sought to identify tissue specific markers that increase the diagnostic accuracy of biopsy material. Here Adley and colleagues present their findings on the ability of kidney specific cadherin (ksp-cad) to differentiate chRCC from oncocytoma. Previous reports on this marker have been mixed. One study using immunohistochemistry demonstrated that it was expressed on 97% of chRCC and only 3% of oncocytomas, whereas another demonstrated no real differences in expression between the two histiotypes.

The authors examined the expression of ksp-cad at both the mRNA (gene array analysis) and protein (immunohistochemistry) level. Examining mRNA levels, the authors looked at 15 chRCC and 15 oncocytomas and found ksp-cad expression in 89% of chRCC and 64% of oncocytomas. Examining protein expression with immunohistochemistry in 36 chRCC and 41 oncocytomas, the authors found expression in 86% of chRCC and 76% of oncocytomas. Of note, expression in these two tumor types was significantly higher than that found in clear cell or papillary renal cell carcinoma.

Kidney specific cadherin joins the growing list of purported specific tissue markers that fail to differentiate chRCC from oncocytoma on further analysis.

Anatomic Pathology 126: 79-85, 2006

Written by Christopher G. Wood, MD, a Contributing Editor with UroToday.

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