Colon cancer and Crohn's disease. Endoscopic view of adenocarcinoma in the transverse colon (part of the large intestine) of a patient with Crohn's disease. An adenocarcinoma is a tumour arising from the cells lining the affected organ. Crohn's disease causes inflammation, thickening, and ulceration (white areas) of the intestinal tract. Its cause is unknown and there is no cure. People with Crohn's disease are at higher risk of developing bowel cancer. Surgical removal of the affected portion of the intestine may be required.