Histological Typing of Urinary Bladder Tumours

The 1973 WHO classification of bladder tumours anticipated a probable need for eventual revision of the criteria for diagnosing papillary and flat bladder neoplasia.

A workshop sponsored by the WHO consisting of pathologists, urologists, cytologists, oncologists and basic scientists interested in bladder tumours addressed this subject, and after a follow- -up meeting sponsored by the International Society of Urological Pathology, the classification and terminology used in this text were agreed upon.

A major change is in the introduction of a new category: papillary urothelial neoplasm of low malignant potential.

Many of the tumours previously designated as papillary transitional cell carcinoma, grade I now fall into that category.

Another major change is in the designation of flat lesions, and this includes a definition of carcinoma in situ.

Furthermore, a number of variant forms of urothelials carcinomas are included as well as new entities not recognized when the 1st edition was issued.