Adenocarcinoma of the colon simulating primary urinary bladder neoplasia. A report of nine cases.

Nine cases of adenocarcinoma of the colon, secondarily involving the urinary bladder mucosa and histologically mimicking primary bladder neoplasia, are reported. Five patients presented with bladder involvement at the time of diagnosis of colon cancer; four developed vesical lesions 9 to 66 months after resection of their colonic primary. The majority (89%) had genitourinary symptoms at presentation; gastrointestinal manifestations were present in only 60% of those with synchronous colonic involvement. The initial clinical impression, largely based on cystoscopic and radiographic studies, was a bladder primary in four cases and colon cancer in five. Of the former, three (75%) were known to have a history of colon cancer. Histologically, all were enteric-type adenocarcinomas and all had features mimicking a villous adenoma of the bladder. Distinguishing a primary bladder adenocarcinoma from spread of a colonic carcinoma to the bladder may not be possible on histopathologic grounds alone. Consideration should be given to the possibility of an extravesical primary even when symptomatology, cystoscopy, radiographic studies, and histopathology suggest a primary bladder neoplasm.