Primary neoplasm in a vesical diverticulum: analysis by step-sectioning.

A primary neoplasm arising in a vesical diverticulum was cystectomized and analyzed by step-sectioning of the whole bladder in an attempt to determine the carcinogenic process. Serial sections of the cystectomy specimen revealed a small area of mild dysplasia in the mucosa of the bladder and the diverticulum without a tumor. Most of the mucosal cells in the tumor-bearing diverticulum were desquamated, but a small area of dysplasia in the remaining cells was also observed.