Human Kidney Injury Molecule-1 (hKIM-1): A Useful Immunohistochemical Marker for Diagnosing Renal Cell Carcinoma and Ovarian Clear Cell Carcinoma

Human kidney injury molecule-1 (hKIM-1), a type I transmembrane glycoprotein expressed in injured renal proximal tubules, was also found in renal cell carcinoma (RCC). The current study attempts to evaluate the diagnostic utility of hKIM-1 in a large series of 480 neoplasms including defined subtypes of renal cell tumors, metastatic RCCs, and nonrenal tumors. Tissue microarray (TMA) sections containing 179 renal cell tumors (73 clear cell RCC, 30 papillary RCC, 16 chromophobe RCC, 15 oncocytoma, and 45 metastatic RCC) were included in this study. In addition, 80 cases of renal cell neoplasm and 221 nonrenal tumors in routine tissue sections were also included. Both TMA and routine sections were incubated with anti-hKIM-1 monoclonal antibody using an EnVision-HRP kit. The results demonstrated that a membranous/cytoplasmic staining pattern for hKIM-1 was observed in 54 of 73 (74%) clear cell RCCs and 28 of 30 (93%) papillary RCCs on TMA sections. Zero of 54 chromophobe RCCs and 4 of 41 (9.75%) oncocytomas were positive for hKIM-1 when combining TMA and routine sections. Similar staining results were observed in 35 of 45 (78%) metastatic RCCs. Data from cDNA microarray expression and Western blot demonstrated similar findings. Fifteen of 16 cases (93.8%) of clear cell carcinoma of the ovary demonstrated positive reactivity for hKIM-1. These data indicate that hKIM-1: (1) is a relatively sensitive and specific marker for papillary, clear cell, and metastatic RCCs, (2) can be used to distinguish clear cell from chromophobe RCC, and (3) may serve as a diagnostic marker for clear cell carcinoma of the ovary.