Mapping of the urinary bladder: its impact on the concepts of bladder cancer.

The results of mapping of the urinary bladder are reported and discussed. It has been shown that Brunn's nests, cystitis cystica, and the vaginal type of squamous metaplasia are commonly found in normal bladders and thus cannot be considered as precancerous lesions. Mapping of cancerous bladders and related histologic and clinical observations strongly suggests that there are two distinct pathways in bladder neoplasia: the papillary pathway and the nonpapillary pathway. Papillary tumors with thin stalks must be considered as a focal expression of the proliferative potential of the urothelium. They are per se quite harmless but may be followed by other manifestations of neoplasia. Broad based papillary tumors, regardless of grade, may have "pushy borders," which extend into the lamina propria but rarely invade the muscularis. Nonpapillary flat lesions, notably atypical hyperplasia and carcinoma in situ, appear to be the principal source of invasive and metastasizing bladder cancer. The presence of the flat lesions puts the patient at high risk for the development of invasive carcinoma. Methods of assessment of the cancerous bladder are suggested and discussed.