Histologic grading of noninvasive papillary urothelial neoplasms

OBJECTIVES: In 1998, a revised system of classifying noninvasive papillary urothelial neoplasms of the urinary bladder was proposed and subsequently formally adopted by the World Health Organization (WHO). The introduction of this new system was justified as being potentially superior on a number of levels to the 1973 WHO classification system that it replaced. Specifically, a new category of neoplasms, designated papillary urothelial neoplasm of low malignant potential (PUNLMP), was considered advantageous for several reasons. The new system was expected to gain widespread acceptance, improve reproducibility of diagnoses among pathologists, and enhance the correlation between urine cytology and tumor histology. We examine the history of the changes in terminology for these lesions, the relative merits of PUNLMP terminology, the extent to which the expectations accompanying the new grading system have been met, and the extent to which the new system has enhanced the management of patients with noninvasive papillary urothelial neoplasms of the bladder. METHODS: A PubMed literature search after the introduction of this new classification was performed and relevant papers reviewed. RESULTS AND CONCLUSIONS: The 2004 WHO classification is a positive initiative in attempting to standardize urothelial tumor grading by expanding and clearly defining the morphologic characteristics of noninvasive papillary urothelial neoplasms. The new terminology used in this system is of questionable validity and utility. Full-genome searches for prognostic and predictive molecular gene expression signatures, GeneChip technology and proteomics techniques, and several new biomarkers and molecular tests may be useful in future grading schemes after their clinical utility is better established.