Clinicopathological features and CD57 expression in renal cell carcinoma in acquired cystic disease of the kidneys: with special emphasis on a relation to the duration of haemodialysis, the degree of calcium oxalate deposition, histological type, and possible tumorigenesis.

AIMS: Acquired cystic disease of the kidney (ACDK) in patients undergoing haemodialysis is known to develop into renal cell carcinoma (RCC), but its pathogenesis remains unclear. The aims were to analyse the histological findings of ACDK-RCC and to determine its histogenesis.

METHODS AND RESULTS: Twenty-nine RCCs in 23 patients with ACDK were classified into three groups according to the duration of haemodialysis and were analysed for histological type, calcium oxalate (Oxa) deposition, and cyst and atypical cyst (AC) formation. Histologically, 21 tumours were ACDK-RCC and eight were clear cell carcinoma (CCC). The ratio of ACDK-RCC and the numbers of cysts and ACs increased as the duration of haemodialysis was prolonged. The degrees of intratumoral Oxa deposition and cyst and AC formation of ACDK-RCCs were higher than those of CCCs (Oxa, P=0.028; cyst, P<0.0001; AC, P=0.0002). Many ACDK-RCCs (85.7%) and some CCCs (50%) had characteristics of the thin ascending loop of Henle as assessed by CD57 (HNK-1) expression, which was rarely expressed in the 29 control cases.

CONCLUSIONS: ACDK-RCCs reveal characteristics of Henle's loop, which may be related to their peculiar pathological features, including intratumoral oxalate deposition and cyst and AC formation.