ISUP/WHO Classification of Papillary Urothelial Neoplasms of Urinary Bladder: Consensus Study Conducted by Korean Society of Urogenital Pathology

ABSTRACT

BACKGROUND: Pathologic grading, one of the most important prognostic factors of papillary urothelial neoplasia (PUN) of the urinary bladder, has been revised continuously. The current study focused on the analysis of interobserver agreement on PUN of the urinary bladder bet- ween 1973 WHO classification (WHO 1973) and 1998 WHO/ISUP classification. METHODS: Seventy five cases from 15 institutions were collected, and after review by Korean Society of Urogenital Pathology (KSUP), 30 cases were selected as follows; group I, WHO grade 1 and papillary urothelial neoplasm of low malignant potential by ISUP (7 cases), group II, WHO grade 2 and low-grade papillary urothelial carcinoma (16 cases), and group III, WHO grade 3 and high-grade papillary urothelial carcinoma (7 cases). Seventy five general surgical pathologists who participated in this study were asked to grade the tumors based on WHO/ISUP classification. Interobserver agreement between the participants' diagnosis and KSUP consensus diagnosis was analyzed by kappa value. RESULTS: Interobserver agreement assessed by kappa value for all diagnostic groups was very low; for group I, kappa value was -0.900893722; for group II, -0.944650025, and for group III, -0.876728996. The overall kappa value of pathology residents was better than that of practicing pathologists. CONCLUSIONS: The 1998 WHO/ ISUP classification could not be easily translated from the 1973 WHO classification and because of poor interobserver agreement, it appears that further work would be needed before it can be practically applied.