Sigmoid colon cancer arising in a diverticulum of the colon with involvement of the urinary bladder: a case report and review of the literature

Abstract

Background: Colon cancer can arise from the mucosa in a colonic diverticulum. Although colon diverticulum is a common disease, few cases have been previously reported on colon cancer associated with a diverticulum. We report a rare case of sigmoid colon cancer arising in a diverticulum with involvement of the urinary bladder, which presented characteristic radiographic images.

Case presentation: A 73-year-old man was admitted to our hospital for macroscopic hematuria. Computed tomography and magnetic resonance imaging revealed a sigmoid colon tumor that protruded into the urinary bladder lumen. The radiographs showed a tumor with a characteristic dumbbell-shaped appearance. Colonoscopy showed a type 1 cancer and multiple diverticula in the sigmoid colon. A diagnosis of sigmoid colon cancer with involvement of the urinary bladder was made based on the pathological findings of the biopsied specimens. We performed sigmoidectomy and total resection of the urinary bladder with colostomy and urinary tract diversion. Histopathological findings showed the presence of a colovesical fistula due to extramurally growing colon cancer. Around the colon cancer, the normal colon mucosa was depressed sharply with lack of the muscular layer, suggesting that the colon cancer was arising from a colon diverticulum.

Conclusion: The present case is the first report of sigmoid colon cancer arising in a diverticulum with involvement of the urinary bladder. Due to an accurate preoperative radiological diagnosis, we were able to successfully perform a curative resection for sigmoid colon cancer arising in a diverticulum with involvement of the urinary bladder.

Figure 1

Enhanced MRI T1-weighted image. Between the sigmoid colon and the urinary bladder, the solid tumor was connected via the fistula, showing a dumbbell-shaped appearance. The sigmoid colon tumor protruded into the urinary bladder lumen (arrows) via the colovescal fistula (arrowheads).

Figure 2

Barium enema findings. The colon tumor was detected as a defect in the sigmoid colon (arrow). Around the sigmoid colon cancer, there were multiple colon diverticula in the sigmoid colon.

Figure 3

Cross section of the resected specimen. A: Macroscopic picture of a cross section. B: Diagram of a cross section. The progression of the sigmoid colon cancer was reflected in the MRI findings. The macroscopic findings revealed the progression via the colovesical fistula. SC: sigmoid colon cancer. UBT: urinary bladder tumor.

Figure 4

Microscopic findings of the resected specimen (H-E staining, ×200). A: The sigmoid colon cancer, penetrating to the urinary bladder, did not invade the surrounding muscular layer as the tumor progressed. Adjacent to the sigmoid tumor, the normal colon mucosa was depressed sharply (arrows) with a thin-walled muscular layer (arrowhead), indicating that the colon cancer had arisen from a colon diverticulum. B: The sigmoid and urinary sides of the tumor were connected via the colovesical fistula. In the fistula, the cancerous tissue was completely covered with fibrous tissue, indicative of no exposure to the intraperitoneal space to cancerous tissue.