Cancer of the descending colon. Gross specimen of an annular tumour causing stenosis (localised narrowing of the alimentary canal). The tumour is an adenocarcinoma, a type of colorectal cancer arising from glandular epithelial tissue. Adenocarcinomas will have developed from adenomas (adenomatous polyps), the benign version of the cancerous tumour. Adenocarcinomas account for about 90-95% of all colorectal cancers, and colon cancer makes up around 10% of all recorded cancer cases in Western societies. Certain dietary habits, such as a diet high in fat, appear to be significant risk factors.