The pathology of bladder cancer

Carcinoma of the bladder is the seventh most common cancer worldwide [1]. It comprises 3.2% of all cancers, with an estimated 260 000 new cases each year in men and 76 000 in women. The highest incidence rates in males and females occur in Western Europe, North America and Australia. The UK annual incidence is over 10 000 new cases, with a male:female ratio of 5 : 2 [2–5]. Urothelial carcinoma is the most common type of bladder cancer. However, there is significant geographic variation, and in certain regions of the world, such as Egypt and parts of Africa, squamous cell carcinoma (SCC) of the bladder predominates. Urothelial carcinomas of the renal pelvis, ureter and urethra are less common, accounting for approximately 10% of all urinary tract neoplasms. It should be noted that the formerly used term ‘‘transitional cell carcinoma (TCC)’’ is now largely replaced by ‘‘urothelial carcinoma,’’ although you will still hear urologists and pathologists use both interchangeably. The WHO histological classification of tumors of the urinary tract (2004) is given in modified form in Table 1.1 [6]. The urothelium is the lining epithelium of the urinary collecting system and includes that of the renal pelvis, ureters, bladder and part of the urethra. Its thickness varies from three to seven cell layers, depending on the state of distension of the bladder. The turnover rate of those cells is low, of the order of three to six months. The cells desquamate but very few cells are seen in normal urine cytology specimens, i.e. normal urine is hypocellular. Very few mitotic figures are seen in normal urothelium. The presence of surface ‘‘umbrella cells’’ indicates normal maturation in the urothelium. These cells are large and elliptical and have abundant eosinophilic