Urologic Pathology: Introduction

Course Map: Introduction

Introduction

Any course about the pathology of the urinary bladder will deal largely with the diagnosis of bladder cancer and the various tumor-like lesion that can be confused with bladder cancer, either in clinical examinations or at the microscope. In doing so, this course follows very closely the format used in the recently revised International Histological Classification of Urinary Bladder Tumours. The text is basically a description of the light microscopic recognition of specific disease processes with additional comments, where appropriate, about necessary special stains and immunohistochemistry.

The new WHO classification differs from the old one chiefly in the sections dealing with papillary and flat lesions. In order to achieve the broadest possible consensus, we invited members of the International Society of Urologic Pathologists and also Urologist to join with the World Health Organization Panel, and the descriptions and definitions dealing with papilloma, papillary carcinoma, in-situ carcinoma, atypia, dysplasia and hyperplasia are properly to be known as the WHO/ISUP Classification. There are two major changes. Tumors will no longer be diagnosed as papillary carcinoma merely because of their propensity to recur - they now must exhibit cytologic anaplasia to merit this designation. This has created a new category, intermediate between the papilloma and the Grade I papillary carcinoma: papillary urothelial neoplasm of low malignant potential. The other major change is in the criteria for diagnosing carcinoma in-situ. Any number of cytologically malignant cells will establish this diagnosis; full-thickness cellular anaplasia is not now required.

We have attempted to offer a more detailed description of the three tumor grades although there will likely always be some subjectivity involved with tumor-grading. We encourage pathologists to recognize, and to incorporate into the diagnosis, the urothelial carcinoma variants and to include, also, the tumor TNM stage.

The epithelium of the urinary tract has traditionally been referred to as transitional epithelium. It is now widely agreed, however, that this is a specific type of epithelium which more accurately should be designated as urothelium. Transitional epithelium and transitional cell carcinoma are still widely used, however, and in this text they are used synonymously with urothelium and urothelial carcinoma.

Lastly, for the maximum benefit of the reader, we have periodically interrupted the text with a short quiz (self-check). At the end there is a more detailed examination.

The bibliography includes a number of general references which will not be cited in the text. These are textbooks and atlases which can be expected to cover most topics dealing with urologic pathology.