Objective: To study the expression and clinical significance of kidney injury molecule-1 (KIM-1) in primary and metastatic renal epithelial neoplasms.
Methods: A total of 136 cases of kidney neoplasms were retrospectively reviewed including 63 primary clear cell renal cell carcinomas (RCCs), 22 papillary RCCs, 13 chromophobe RCCs, 7 oncocytomas, 7 RCCs associated with Xp11.2 translocation/TFE3 gene fusions and 24 metastatic clear cell RCCs. Immunostaining for KIM-1 and kidney-specific-protein (Ksp)-cadherin were performed and the relationship to tumor stage and grade in clear cell RCCs was investigated.
Results: Expression of KIM-1 was detected in 77.8% (49/63) of clear cell RCCs, 90.9% (20/22) of papillary RCCs, 1/13 of chromophobe RCCs, 7/7 of RCCs associated with Xp11.2 translocation/TFE3 gene fusions and 87.5%(21/24) of the metastatic RCCs, but not detected in 7 cases of oncocytomas. A diffuse expression of KIM-1 was more frequently observed in Furhman nuclear grade III/IV clear cell RCCs (P = 0.010). Ksp-cadherin expression was mainly observed in chromophobe RCCs and oncocytomas.
Conclusions: KIM-1 is a specific biomarker for injuried kidney proximal tubules and the corresponding neoplasms, and has a high specificity and sensitivity for primary or metastatic clear cell RCCs, papillary RCCs and RCCs associated with Xp11.2 translocation/TFE3 gene fusions. Combination of KIM-1 and Ksp-cadherin immunostaining can lead to a more precise histological classification of primary kidney epithelial neoplasms and improve the diagnostic accuracy of metastatic RCCs.