Bladder cancer is the fifth most common male cancer among Americans. Almost all bladder cancer in the United States is composed of transitional cell carcinoma. Familial cases are rare and usually part of the Lynch syndrome. Smoking is perhaps the greatest risk factor for sporadic disease.

Cytogenetic studies have identified a number of chromosomal changes in bladder cancer. Low-grade noninvasive tumors are usually diploid, whereas high-grade invasive tumors often contain gross aneuploidy. Monosomy of chromosome 9 is the most common abnormality seen in this disease.

Few proto-oncogene mutations or amplifications have been described in bladder cancer. However, chromosomal deletions are very common on chromosomes 9p, 17p, and 13q. Candidate genes inactivated at these loci include p16, p53, and Rb, respectively. Moreover, p53 and Rb mutations usually are seen in flat (carcinoma in situ) or invasive lesions and are correlated with a poor prognosis.

Many bladder cancers appear as multifocal disease at presentation. Molecular studies have shown that multiple tumors in the same patient arise from the uncontrolled spread of a single progenitor cell. These tumors then proceed through variable genetic events during progression. A preliminary molecular progression model for bladder cancer suggests that chromosome 9p is an early loss event in most tumors. Conversely, loss of chromosomes 17p and 14q is more often associated with flat lesions and invasive tumors.

Genetic alterations can be detected in the urine sediment of patients with bladder cancer. Microsatellite analysis allows detection of loss of heterozygosity (LOH) or genomic instability in primary tumor and urine DNA. Pilot studies suggest that most bladder tumors can be detected by DNA analysis. Moreover, these approaches are amenable to automated techniques suitable for the clinical setting.