Immunohistochemical evaluation of aldose reductase expression in collecting duct carcinoma for differential diagnosis from other renal malignancy.

Abstract

483 Background: Collecting duct carcinoma (CDC) is a rare tumor but its recognition is important for the prediction of prognosis and decision making of the treatment. However, its diagnosis is challenging because of versatility of pathological features. We explored the possibility whether aldose reductase (AR), osmoregulatory protein and abundant in renal medulla, can be used as a marker for the pathologic diagnosis of CDC. Methods: We prepared anti-AR monoclonal antibodies, examined expression of AR protein in the human normal kidney. Immunohistochemical expressions of AR, 34bE12, a-methyl CoA racemase (AMACR) and expressions of lectins (Ulex europaeus agglutinin 1; UEA-1 and peanut agglutinin; PNA) were examined on normal kidney, 12 cases of CDC, 10 cases of papillary renal cell carcinoma (pRCC), and 10 cases of invasive urothelial carcinoma (iUC). Results: AR 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, AR was strongly positive in 9 of 12 CDC cases. AR was negative in cases of either iUC or pRCC. In contrast, although lectins were positive in all cases of CDC, they were also found in all types of malignancy. iUC was positive for 34bE12 in all cases but also so in some cases of CDC and pRCC. AMACR was positive for all the cases of pRCC but also positive for other tumors. Conclusions: Compared with other markers, AR may be a more specific and potentially useful marker for CDC. [Table: see text]