Urinary Bladder Nephrogenic Adenoma: A Histopathological Case Report.

Nephrogenic adenomas are benign lesions that develop within the urinary tract. Most often developing within the urinary bladder, these lesions have a debatable etiopathogenesis, with hamartoma, rest hyperplasia, and transplantation of renal tubular cells being the most widely accepted ones. Nephrogenic adenomas develop more often in adult males, and predisposing factors for their development are prior urinary system injury, infection, or malignancy, with a subset of cases developing in renal transplant patients. Herein, we present a case of a male patient in his seventies who initially presented to our institution with urinary disturbances and was subsequently diagnosed with low-grade, non-invasive urothelial carcinoma. After treatment, the patient remained disease-free for a period of seven calendar years. The current presentation was due to dysuria, and bladder endoscopy revealed a ureteral stricture and two small exophytic lesions neighboring the location of the previously treated urothelial carcinoma. Histology revealed complex papillary architecture and cystic spaces lined by a monolayer of monomorphous epithelial cells with foci of hobnail appearance. The papillary stroma consisted of edematous fibrous tissue with hyperemic blood vessels and focal infiltration by inflammatory cells. Based on the histological findings, the diagnosis of nephrogenic adenoma was established.