Invasive bladder cancer merging with synchronous rectal cancer which demonstrated bladder invasion: A case report

A 75-year-old man had the complaints of dyschezia and dysuria. Colonofiberscopy was performed, revealing an irregular mass all around the rectosigmoid wall. He was referred to our hospital as a case of rectal cancer. Abdominal CT suggested bladder invasion, and cystoscopy demonstrated extensive edematous mucosa. Urine cytology was class V (adenocarcinoma), and we diagnosed the case as rectal cancer with direct invasion to the bladder. We performed low anterior resection of the rectosigmoid colon with en bloc cystoprostatectomy, and subsequently colorectal anastomosis and ileal conduit urinary diversion. Histopathological examination showed two distinct primary malignancies. One was adenocarcinoma of the rectum with direct invasion to the bladder, and the other was urothelial carcinoma of the bladder (G3, pT4). The two cancers had no contact with each other, either in the bladder wall or in the epithelium. To our knowledge, this is the fourth case of bladder cancer merging with synchronous rectal cancer which demonstrated bladder invasion.