A cribriform urothelial neoplasm of the renal pelvis: an adenoid cysticlike variant of inverted urothelial papilloma or florid ureteritis cystica?

Tumors with cribriform appearance, similar to that of salivary gland adenoid cystic carcinoma, have been described at various anatomic sites. We present an unusual polypoid tumor, discovered incidentally, in the renal pelvis of an elderly man. The mass displayed a prominent cribriform architecture, akin to adenoid cystic carcinoma with an immunophenotype that supported a urothelial origin. Because of its lack of significant invasive growth and other adverse morphologic features, this lesion will likely behave in a banal fashion. This cribriform urothelial neoplasm of the renal pelvis may, in fact, represent a variant of an inverted urothelial neoplasm with a prominent cystic component or florid ureteritis cystica. It is important for pathologists to recognize this growth pattern as a possible variant of urothelial tumors.