Expression of Aldo-keto-reductase 1B1 (AKR1B1) in tubulocytic carcinoma of kidney.

Abstract

507 Background: Tubulocystic carcinoma of the kidney (TubCC) is a new entity of tumor not listed in the 2004 WHO classification. The tumor comprised tubules forming duct-like structures exhibiting hobnail change, and resembled collecting duct carcinoma (CDC) by immunostaining; thus, this tumor was named low grade CDC. Since then, similar tumors have been reportedly called tubulocystic carcinoma (TubCC)We explored the possibility whether Aldo-keto-reductase-1B1 (AKR1B1), osmoregulatory protein and abundant in collecting duct, can be used as a marker for the pathologic diagnosis of TubCC. Methods: We prepared anti-AKR1B1 monoclonal antibodies, examined expression of AKR1B1 protein in the human normal kidney. Immunohistochemical expressions of AKR1B1 was examined on normal kidney, 4 cases of TubCC, 10 cases of papillary renal cell carcinoma (pRCC), and 10 cases of invasive urothelial carcinoma (iUC). Results: AKR1B1 expression distributed preferentially in the renal medulla and not in the cortex, reflected by its high concentration in medulla (2.12 ±1.35 μg/mg) compared with cortex (0.13 ± 0.03 μg/mg). Immunohistochemically, AKR1B1 was strongly positive in 3 of 4 TubCC cases. AKR1B1 was negative in cases of either iUC or pRCC. Conclusions: Although the present study was small and preliminary, AKR1B1 may be a more specific and potentially useful marker for TubCC. [Table: see text]