WHO/ISUP Classification of Papillary Urothelial Tumors: have We Finally Settled for it?

Abstract

Histological grading of noninvasive papillary urothelial tumors is the most important prognostic factor short of tumor invasion. Various schemes and classifications have been proposed since last few decades, all based on morphological criteria alone. Among these, 1973 WHO classification proved very successful in clinical practice and dominated for almost three decades. In late 1990s efforts were initiated to reevaluate and reassess the grading schema and these efforts resulted in the promulgation of WHO and International Society of Urologic Pathologists (ISUP) classification of noninvasive urothelial neoplasms in 1998. This classification was further refined and published in the latest WHO blue book on Pathology and Genetics of Tumours of the Urinary System and Male Genital Organs as 2004 WHO classification. The later classification has however not completely replaced the 1973 WHO classification and many centers are using both the classifications in the pathology report. It is time to incorporate immunohistochemical, molecular genetic and omics data to further refine this prognostic classification.