Simultaneous occurrence of transitional cell carcinoma and urothelial adenocarcinoma associated with xanthogranulomatous pyelonephritis.

We report on a patient with xanthogranulomatous pyelonephritis, in situ transitional cell carcinoma, and focal prosoplasia revealing abrupt conversion of transitional epithelium to moderately well-differentiated adenocarcinoma. The etiology and pathogenesis of mucinous adenocarcinoma in the renal pelvis very likely involves the prosoplastic transition of pre-existing transitional carcinoma to adenocarcinoma. The urologist should be aware of the increased possibility of this tumor developing in a patient with longstanding infection, and frozen section should be performed more often because the gross structure of the tumor frequently appears normal. This permits the urologist to change his surgical strategy if frozen section is positive for tumor.