Urinary tract villous adenomas are uncommon tumors. These have been mostly described in the urinary bladder and uncommonly in the urethra, prostate, vagina and vulva.[3
] So far, only two cases involving the upper urinary tract have been described in the English literature. Chronic irritation due to a calculus or infection leads to intestinal metaplasia of the urothelium and mucus production. As there is some obstruction usually, mucosuria may not be present. Cystitis glandularis and enteric type of epithelium are considered precursors of these changes. Our specimen showed only diffuse intestinal metaplasia of renal pelvis with villous adenoma of the pelvicaliceal system and a solitary adenoma of the upper ureter. Histopathological examination of the specimen showed villous adenoma with presence of basally located nuclei of simple mucus tall, columnar epithelium and goblet cells amongst the villiform glands. Like other villous adenomas, urinary tract villous adenomas also are CK20 and CEA positive. CK7 positivity is found in about 50% of urinary tract tumors.[3
The term muconephrosis was first used by Park and associates to describe a case of renal pelvic villous adenoma with mucus-filled kidney. A local extension from intestinal adenocarcinoma should be ruled out in all these patients. Whenever a diagnosis of villous adenoma is made, it behooves the pathologist to make a thorough sampling of a lesion to diagnose a coexisting adenocarcinoma and extension of tumor from nearby structures.