Carcinoma in situ spread to mucosa of sigmoid colon neobladder

This is the first case of carcinoma in situ (CIS) of a transitional cell carcinoma that had spread into a neobladder constructed using a bowel segment associated with local recurrence at the ureteral-neobladder anastomosis. Considering that the CIS lesion was found in macroscopically intact epithelium remote from the main tumor, this strongly suggests that CIS could arise from solid tumor by implantation. Although some studies have reported secondary malignancy occurring in the neobladder, most have been adenocarcinoma that arose from the replaced bowel segment. To our knowledge, the present case is the first of widespread CIS of transitional cell carcinoma in an orthotopic neobladder.