Upper respiratory tract villous adenoma (VA) with muconephrosis is rare and should be included in the differential diagnosis when pelvic dilatation with a solid component is detected. VA may transform into malignant mucinous adenocarcinoma, which should be suspected if contrast enhancement on computed tomography (CT)/magnetic resonance imaging (MRI) and restricted diffusion on MRI are observed.

Villous adenoma is a rare tumor in the urinary system that usually occurs in the bladder. It is extremely uncommon in the renal pelvis. Most of the previously reported cases have been diagnosed with severe hydronephrosis associated with renal parenchyma atrophy prior to surgery. Because of its rarity, available information on the pathogenesis, diagnosis, treatment and prognosis of the disease is limited. We reported a case of kidney stones with hydronephrosis. During percutaneous nephroscopic lithotripsy, a renal pelvis tumor was found. Biopsy confirmed that the tumor was a villous adenoma of the renal pelvis.

A 68-year-old female was admitted to the hospital due to right kidney stones with right hydronephrosis. After admission, a urinary system plain computed tomography scan was performed, which revealed right kidney stones with right hydronephrosis and right upper ureteral dilatation. Multiple new cauliflower-like papillary masses were then discovered in the renal pelvis and calyces during right percutaneous nephroscopic lithotripsy. Biopsy results indicated villous adenoma with high-grade glandular intraepithelial neoplasia. The patient underwent laparoscopic radical resection of the right kidney and ureter. Based on histopathological and immunohistochemical examination, the patient was diagnosed with villous adenoma without adenocarcinoma.

Villous adenoma is rare in the urinary system. We reported a case of renal pelvis villous adenoma, which may provide useful information for the early diagnosis and treatment of this tumor.