A Case of Sigmoid Colon Cancer Probably Originated from a Diverticulum

Abstract

A 64-year-old man presented to our hospital because of a positive fecal occult blood test result at a medical checkup. A colonoscopy showed edematous stenosis without a tumorous lesion in the sigmoid colon. A CT scan showed a low-density mass containing air bubbles in the sigmoid colon. MRI showed the mass to be isointensity as muscle in T1-weighted images, a slightly higher intensity than muscle in T2-weighted images, and a higher intensity in Diffusion-weighted images. FDG-PET showed an abnormally high accumulation of FDG in the sigmoid mass. Thus, sigmoid colectomy with D3 lymphadenectomy was performed on the diagnosis of suspicious sigmoid colon cancer. Histological examination showed mucinous carcinoma invading the subserosal layer of the sigmoid colon (pT3, N0, M0, Stage II), and carcinoma in situ in a sigmoid diverticulum, suggesting that the carcinoma might have originated from the diverticulum. Considering the aging of the general population and lifestyle changes in Japan, we should pay attention to the risk of developing cancer from diverticula of the left colon.