OBJECTIVETo explore the clinicopathological features, immunophenotype, differential diagnosis, pathogenesis and prognosis of villous adenoma with poorly differentiated adenocarcinoma of the urinary tract.

METHODSClinical and pathologic findings of 3 cases of villous adenoma with poorly differentiated adenocarcinoma of the urinary tract were analyzed by gross examination, microscopic investigation and immunohistochemical staining. The related literatures were reviewed.

RESULTSAll of the three cases were middle-aged or elderly patients. Three cases all presented with hematuria and mucusuria. Endoscopic examination identified that case 1 had a polyp with broad attachment in the dome of bladder, case 2 had a solid mass in the ureter, and case 3 had a exophytic fungating tumor in the renal pelvis. Microscopically, case 1 revealed a papillary lesion with finger-like processes lined by pseudostratified columnar epithelium with abundant goblet cells. The cells demonstrated moderate degree dysplasia. In case 2 and case 3, both villous adenomas and poorly differentiated adenocarcinoma were observed, the adenoma cells arranged in a cribriform pattern, and the tumor cells showed severe atypia, mitotic activity, and transition with invasive poorly differentiated adenocarcinoma. Immunohistochemically, the tumor cells in three cases were positive for CK20, CEA,EMA and MUC-1; none of them expressed cdx-2 and PSA; In case 2 and 3, the same immunophenotype of villous adenomas and their associated adenocarcinomas was observed, but the number of the positive cells of p53 and Ki-67 staining were significantly increased in the area of adenocarcinomas than in that of the villous adenomas.

CONCLUSIONSVillous adenoma of the urinary tract is rare. It can occur in the urinary bladder, urachus, renal pelvis, ureter and urethra. These lesions may have malignant potential and frequently coexist with other malignant tumors. So, villous adenoma of the urinary tract should be removed completely and sampled thoroughly to avoid missing a more aggressive component.