Intestinal-Type Villous Adenoma of the Urinary Bladder Presenting as an Asymptomatic Diffuse Plaque-Like Trigonal Lesion: A Rare Case With Multimodal Clinicopathologic Correlation

Villous adenoma of the urinary bladder is a rare, benign glandular neoplasm with intestinal differentiation.This neoplasm is frequently associated with chronic urinary irritation and intestinal metaplasia of the urothelium.Fewer than 50 cases have been documented, and limited information is available regarding its clinicoradiologic spectrum.A 51-year-old man with severe anemia was found to have multiple broad-based exophytic lesions of the bladder on ultrasound.There was no hematuria, mucosuria, or other lower urinary tract symptoms.A minimally enhancing, plaque-like lesion measuring approximately 5 × 1 cm was observed in the trigone and extended to both vesicoureteric junctions.CT urography showed no obstruction or invasion by the lesion.Cystoscopy revealed a velvety, villiform lesion involving the bladder base, and complete transurethral resection was performed.Histopathological examination showed an intestinal-type villous adenoma composed of papillary and villous fronds lined by pseudostratified columnar epithelium with goblet cells, arising in a background of extensive cystitis cystica et glandularis with intestinal metaplasia and focal highgrade dysplasia.No invasive carcinoma was identified.Follow-up cystoscopy at six months demonstrated no recurrence.To the best of our knowledge, this represents the first reported case of an entirely asymptomatic intestinaltype villous adenoma presenting as a diffuse, plaque-like trigonal lesion extending across both vesicoureteric junctions.This case provides further support for the hypothesis of a bladder carcinogenesis pathway involving an irritation-metaplasia-adenoma sequence.Although these lesions have benign histological appearances, they warrant complete histological evaluation and follow-up because of their documented predisposition to developing synchronous or metachronous malignant lesions.This case emphasizes the importance of complete histological evaluation and continued follow-up.