Noninvasive papillary urothelial neoplasia (NIPUN): Renaming cancer

Papillary urothelial neoplasm of low malignant potential (PUNLMP) terminology remains controversial given its reported recurrence rate, its low interobserver diagnostic reproducibility, and its morphologic and molecular genetic overlap with low-grade noninvasive papillary urothelial carcinoma. By contrast, referring to any noninvasive tumor as a "carcinoma" is also controversial. PUNLMP and low-grade noninvasive papillary urothelial carcinomas cannot be reliably distinguished from one another even by experienced pathologists. As both tumors are treated in an identical manner and have similar rates of recurrence and progression, attempting to make this distinction is unnecessary and of little clinical value. These tumor types should therefore be combined into a single category for grading purposes. We propose that all tumors currently classified as either PUNLMP or low-grade noninvasive papillary urothelial carcinoma be termed low-grade noninvasive papillary urothelial neoplasms (NIPUN). This could improve interobserver reproducibility without sacrificing the prognostic utility of histologic grading. PUNLMP terminology should be discontinued and the term "carcinoma" should be reserved only for tumors showing histologic evidence of invasion.