Villous adenoma of the urinary tract: a report of 23 cases, including 8 with coexistent adenocarcinoma.

Villous adenoma originating in the urinary tract is uncommon. We present the first study of a large number of cases of villous adenoma of the urinary tract with clinical follow-up. Our series consisted of 15 patients with isolated villous adenoma and 8 patients with coexistent adenocarcinoma. The tumors occurred in elderly patients and had a predilection for the urachus, dome, and trigone of the urinary bladder. The typical clinical presentation was hematuria and irritative symptoms, and endoscopic examination usually identified a tumor growth. There was no gender predominance. Light microscopic examination showed morphologic similarity to colonic villous adenoma in all cases. Each tumor was composed of pointed or blunt finger-like processes lined by pseudostratified columnar epithelium. The epithelial cells displayed nuclear stratification, nuclear crowding, nuclear hyperchromasia, and occasional prominent nucleoli and mitotic figures. There was intense carcinoembryonic antigen immunoreactivity on the luminal surfaces (89%). Most cases (78%) contained cytoplasmic acid mucin, demonstrated by Alcian blue periodic acid-Schiff stain. Cytokeratin 20 was positive in all cases, cytokeratin 7 was positive in 56% of cases, and epithelial membrane antigen was positive in 22% of cases. Recurrence or invasive adenocarcinoma did not develop in any patient with isolated villous adenoma during a mean follow-up of 9.9 years. Lung metastasis developed in one patient with coexistent adenocarcinoma and multiple recurrences in another (mean follow-up, 3 years). We conclude that the prognosis is excellent in patients with isolated villous adenoma, and complete surgical resection is curative. Patients with coexistent adenocarcinoma may experience recurrence or distant metastasis, and more aggressive treatment may be indicated.