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.

This revision of the book originally published in 1980 is the result of a collaboration among scientists from 10 countries. The authors include not only pathologists but also a urologist and a basic scientist. The second edition - containing 146 colour photographs - is considerably more extensive than its predecessor. A number of new entities, unrecognized in 1980, are included: prostatic intraepithelial neoplasia, which is commonly associated with carcinoma and may also be seen in a biopsy for elevated PSA; basal cell carcinoma; small cell carcinoma; paracrine-endocrine elements; variants of carcinoma; and stromal sarcoma. The criteria for the diagnosis of carcinoma have been expanded, including the minimal criteria. The Gleason grading system, based on growth pattern, is presented in detail. The WHO grading system, based on nuclear anaplasia and glandular differentiation, is more clearly defined.