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 classification is based primarily on the microscopic charac- teristics of tumours and, therefore, is concerned with morpho- logically identifiable cell types and histological patterns, as seen with conventional light microscopy. The term tumours is used synonymously with neoplasm. The phrase tumour-like is applied to lesions which resemble neo- plasms, clinically or morphologically, but do not behave biologi- cally in a neoplastic manner. They are included in this classifica- tion because they give rise to problems in differential diagnosis and because of the unclear borderline between neoplasms and certain non-neoplastic lesions. Synonyms are listed only if they have been used widely, or if they are considered to be helpful to the understanding of the lesion. In such cases, the preferred term is given first, followed by the synonym. Although the emphasis of this classification is on histological typing, in the examination of kidney tumours, consideration should be given to the degree of cellular anaplasia, the extent of local spread, vascular and lymphatic invasion, and the occur- rence of metastasis. The scheme of histological grading suggested here is as fol- lows: Grade I applies to the tumours that have the least degree of cellular anaplasia compatible with a diagnosis of malignancy; . grade II! applies to tumours with the most severe degrees of cel- lular anaplasia; and grade I! applies to those tumours in be- tween. This scheme is applicable to the carcinomas of the renal parenchyma and pelvis.

This classification is based primarily on the presence of morpho- logically identifiable cell types and growth patterns that can be correlated with the clinical behaviour of the tumour and, in some cases, with tumour markers in the serum. Although some of the histological terms and definitions have histogenetic impli- cations, this classification is not meant to be histogenetic. The terminology adopted for individual tumours is based on their general acceptance and world-wide usage. Synonyms are includ- ed only if they have been widely used in the literature or if they are considered helpful in understanding the lesions. Controver- sial histogenetic terms have been avoided whenever possible. The term tumour is used synonymously with neoplasm. The term tumour-like is applied to non-neoplastic lesions which clin- ically or morphologically resemble neoplasms; they are included in this classification because of their importance in differential diagnosis. Because of the many similarities between testis tumours and those of the ovary, an attempt has been made to follow the WHO histological typing of ovarian tumours. Histological Classification of Testis Tumours 1 Germ Cell Tumours 1.1 Precursor lesions - intra tubular malignant germ cells 1.2 Tumours of one histological type (pure forms) 1 1.2.1 Seminoma ...906113 1.2.1.1 Variant - Seminoma with syncytiotrophob- stic cells 1.2.2 Spermatocytic seminoma ...9063/3 1.2.2.1 Variant - Spermatocytic seminoma with sarcoma 1.2.3 Embryonal carcinoma ...9070/3 1.2.4 Yolk sac tumour ...907113 Polyembryoma ...

During the past decade there has been an increasing awareness of the need for a different approach to the problem of bilharziasis. We do know that 180-200 million people are infected and that the infection is increasing but we have not as yet been able to answer the question: Are they suffering from a disease. Study of vital statistics or hospital records, mass biochemical or immunological tests and community surveys have not yet provided the full answer. Gradually and perhaps begrudgingly, we have come to realize that we must study the ma- initially by means of well controlled clinical observations to obtain evidence for the altered physiology, if any, due to bilharzial infection; secondly and equally important through pathological studies on individual patients to determine the structural changes, if any, as a result of infection with this parasite; and by post mortem studies. Experimental studies of bilharzial infection in animals, valuable as they may be for the elucidation of the pathogenesis of the lesions in the laboratory animal and in man cannot serve as a substitute for the precise information on the nature of the possible lesions induced by bilharziasis in man. Basically, the significance of any clinical observation can 'be evaluated only through reliable pathological confirmation.