Most colorectal cancers arise from polyps, specifically adenomatous polyps. A polyp is a mass of abnormal cells on the surface of the colon or rectum. Polyps can be classified as non-cancerous such as neoplastic hamartoma, a hyperplastic polyp, or an adenomatous polyp. In general, adenomatous adenomas are considered premalignant (can turn into cancer), and although common, only a small percentage (<1%) of adenomatous polyps evolve into cancer.
Up to 25% of patients with colorectal cancer have a family history of the disease, suggesting a hereditary pre-disposition. In addition to heredity, there are other factors like diet, smoking, and diseases such as inflammatory bowel disease that can increase risk of developing colorectal cancer.
Depending on the location of the tumor, symptoms can vary from no symptoms to a variety of different symptoms. These include chronic slow blood loss that cannot be seen with the naked eye; more rapid and obvious blood loss; or obstruction with decreased, and in some cases, inability to pass stool accompanied with abdominal pain.
Treatment for colorectal cancer can include surgery, chemotherapy, radiation therapy, and newer biologic targeted therapy. Like so many other cancers, the initial stage correlates strongly with the risk of recurrence, as well as the choice and outcome of treatments. The earlier colorectal cancer is diagnosed, the more likely it can be cured.