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.
The second edition of this book is the result of collaborative efforts of pathologists from 9 countries. It is more extensive than the previous edition published in 1977. The basic historical classification of the various categories has been retained since it has gained world-wide popularity. The individual categories have been described in more detail. A number of new entities have been included: placental site trophoblastic tumor, large cell calcifying Sertoli cell tumour, cystic granulosa cell tumour of infancy, mixed germ cell sex cord/gonadal stromal tumour, unclassified, tumor of ovarian epithelial type, testicular lesion of adrenogenital syndrome, and testicular lesion of androgen insensitivity snydrome.