Colon cancer. Colonoscope (endoscope) view of a colonic cancer (adenocarcinoma) in a 61 year-old woman. An adenocarcinoma is a cancer that arises from the glandular tissue of an organ's epithelium (lining). The tumour has blocked the sigmoid colon, the final part of the colon, which resulted in abdominal pain and rectal bleeding. Colon cancer, common in the developed world, is thought to be linked to a high-fat and low-fibre diet. Although surgical removal of the affected area may effect a cure if caught early, in this case the cancer had spread (metastasis) to the liver resulting in a poor prognosis.