In most people, colorectal cancers develop slowly over a period of several years. Before a cancer develops, a growth of tissue or tumor usually begins as a non-cancerous polyp on the inner lining of the colon or rectum. A tumor is abnormal tissue and can be benign (not cancer) or malignant (cancer). A polyp is a benign, non-cancerous tumor. Some polyps can change into cancer but not all do. The chance of changing into a cancer depends upon the kind of polyp:1. Adenomatous polyps (adenomas) are polyps that have the potential to change into cancer. Because of this, adenomas are called a pre-cancerous condition
2. Hyperplastic polyps and inflammatory polyps, in general, are not pre-cancerous. But some doctors think that some hyperplastic polyps can become pre-cancerous or might be a sign of having a greater risk of having adenomas and cancer, particularly when these polyps grow in the ascending colon.
3. Dysplasia is another kind of pre-cancerous condition, where an area of the cells in the lining of the colon or rectum looks abnormal (but not like true cancer cells) under a microscope. These cells can change into cancer over time. Dysplasia is usually seen in those who have had diseases such as ulcerative colitis or Crohn’s disease, which cause chronic inflammation of the colon, for many years.