Usually initial damage to the DNA is caught and repaired before the injured cell is transformed into a cancer cell. However, if circumstances place the body at risk, these abnormal cancer cells can begin to grow uncontrollably and eventually compete with normal digestive tract cells for oxygen and nutrients. The growth of these abnormal cells forms excess tissue, known as a tumor, which can invade healthy normal tissue. An additional risk occurs when the abnormal cells break off from the tumor, traveling and growing in other parts of the body. This is called metastasis.
Colorectal cancer can have all the features that are present in other cancers.
Over a period of several years, polyps may grow larger and become cancerous. The exact causes of colorectal cancers are not known. However, there are several factors that increase one's risk of getting this disease. Of these risk factors , some can not be changed, such as age. As we get older, odds increase that cancer may develop.