2004 World Health Organization Classification of the Noninvasive Urothelial Neoplasms: Inherent Problems and Clinical Reflections

Abstract Introduction, evidence acquisition and evidence synthesis The 2004 World Health Organization (WHO) classification of tumors of the urinary system (ie, 2004 WHO classification) subdivides the noninvasive urothelial neoplasms into three major groups—flat, endophytic and papillary—depending on the relationship with the surface of the surrounding urothelial mucosa. Each lesion of these three groups is defined with strict morphologic criteria to provide more accurate information to urologists and oncologists in managing patients. Conclusions There still is debate in the literature as to whether the 2004 WHO classification should be the only one used and whether the 1973 WHO system should be abandoned. Reporting both grades has been recommended.