Urinary Bladder Pathology: World Health Organization Classification and American Joint Committee on Cancer Staging Update.

CONTEXT.—: Since the publication of the previous World Health Organization (WHO) Classification of Tumours on the Pathology and Genetics of Tumours of the Urinary System and Male Genital Organs in 2004, significant new knowledge has been generated regarding the pathology and genetics of bladder neoplasia. Publication of the 2016 WHO "Blue Book" has codified that new data into updated recommendations for classification and prognostication. Similarly, the recent release of the 8th edition of the American Joint Committee on Cancer (AJCC) Cancer Staging Manual, which was implemented in January 2018, has also addressed staging criteria for bladder cancer in several unique settings to clarify their application. OBJECTIVE.—: To highlight subtle changes within the recent WHO and AJCC publications that may affect daily surgical pathology practice. DATA SOURCES.—: Peer-reviewed published literature, the 2016 WHO Classification of Tumours of the Urinary System and Male Genital Organs, and the 8th edition of the AJCC Cancer Staging Manual were reviewed. CONCLUSIONS.—: Selected changes and/or clarifications are discussed and include classification of flat and papillary urothelial neoplasia, select variant patterns of invasive urothelial carcinoma, staging of invasive carcinoma in bladder diverticula, and staging of carcinomas involving the prostate gland.