Immunochemical and molecular assessment of urothelial neoplasms and aspects of the 2016 World Health Organization classification.

The new World Health Organization classification of tumours of the urinary system and male genital organs (4th edn) has several changes from previous versions, and was published in January 2016. New pathways have been discovered in the development of bladder cancer, and were included in this new classification. Guidance from the International Collaboration on Cancer Reporting (ICCR) helped to clarify open questions, in conjunction with the new classification. The histological groups of urothelial carcinoma evolved. Grading remained the same, despite controversy among European urologists. Substaging of pT1 tumours is recommended for the first time, and the ICCR has made recommendations on how to report this. Furthermore, worldwide advice has been published on the use of immunohistochemistry, and recommendations have been made to try to standardize the handling of bladder cancer from a histopathological point of view. At a molecular level, bladder cancer groups have been stratified, and an upcoming molecular classification permits a novel view of this malignancy. This review will try to summarize the most important changes.