Bladder cancer staging

Bladder cancer is a common tumour of the urinary tract, accounting for 6±8% of all male malignancies and 2±3% of all female malignancies [1,2]. In south-eastern England, there were 3000 new registrations in 1992 and over 2000 deaths were reported in 1994 [2]. Bladder cancer is generally considered a disease of later life, reaching a peak incidence in the sixth and seventh decades, although recent trends have revealed an increasing number of younger patients presenting with the disease [3]. The epidemiology of bladder cancer shows strong associations with some environmental factors. An increased incidence of bladder cancer was noted in those working with aniline dyes over 100 years ago. Since then, aromatic amines have been shown to be associated with the development of bladder cancer, introducing an occupational hazard for workers involved with organic chemicals, rubber and paint materials. Diesel fumes and long-term use of the analgesic phenacetin have also been implicated in the development of the disease [4]. Cigarette smoking has an important association with urothelial cancer; cigarette smokers are two to six times more likely to develop the disease than those who do not smoke [5,6]. Cystitis and chronic urinary tract infection predispose to bladder cancer, and < 7% of bladder tumours occur within diverticula. Where schistosomiasis is endemic, there is a high incidence of epithelial tumours, mostly of squamous cell type [7,8]. There is a genetic predisposition to the development of bladder cancer [9]. The clinical presentation of bladder cancer is classically with painless haematuria. Initial diagnostic manoeuvres do not involve imaging. Bacteriological and cytological examination of the urine frequently give signi®cant clues. Further investigation may be directed at the lower urinary tract, when cystoscopy is used. Imaging of the upper urinary tract involves a combination of crosssectional techniques and IVU. The vast majority of bladder tumours are epithelial in origin; of these < 90% are TCCs, the remainder being squamous cell carcinoma, adenocarcinoma and mixed tumours. A wide variety of nonepithelial tumours may affect the bladder. Leiomyosarcoma, rhabdomyosarcoma, phaeochromocytoma, hamartomatous malformations, lymphoma and metastases have been described. The imaging features of these rare tumours have been described only occasionally, but most present as a mass lesion which cannot be reliably discriminated from epithelial cancers using appearances on imaging alone. Of nonepithelial tumours, only lymphoma is suf®ciently common to be seriously considered in the differential diagnosis of a bladder wall mass. The other clinical circumstance which must be considered is that other pelvic tumours may invade directly into the bladder (e.g. carcinoma of the colorectal region, cervix and prostate). The imaging features of primary bladder tumours are essentially not speci®c; the diagnosis must always be con®rmed by cytology or histology, and imaging therefore plays a limited role at the time of diagnosis. Before computer-based cross-sectional imaging became available, mucosal lesions of the bladder could be detected with studies such as IVU, or cystography in which the bladder was ®lled with contrast medium, but the depth of invasion through the wall could not be assessed. With the advent of CT and ultrasonography (US) in the 1970s, and MRI in the 1980s, the penetration of epithelial tumours through the bladder wall can be depicted. Staging of tumours by imaging has become increasingly important in the management of bladder cancer as the available equipment has become more sophisticated. A variety of treatments now exist for bladder cancer and a rational choice is assisted by information from imaging studies. Accurate staging not only allows optimal treatment to be selected for the individual patient, but also allows valid comparisons to be made between different treatments given to patients with disease of similar stage. Some patients can still be staged by clinical means alone, but in most cases, some consideration should be given to the use of imaging as an adjunct.