Urine cytology in the detection of bladder cancer: a critical approach.

Bladder cancer is composed of a group of tumors heterogeneous with respect to configuration, degree of differentiation, and biological course. Lethal and nonlethal forms of the disease exist. The nonlethal forms of cancer are generally well differentiated and not readily detected by voided urine cytology. The lethal form of cancer is accurately detected by voided urine cytology in symptomatic patients, but current evidence indicates a very short preclinical phase for most cases. A screening program should concentrate on detection of the lethal form of bladder cancer.