The colon, also known as the large intestine, is the final portion of the digestive tract and consists of a tube (called the lumen) lined by specialized cells called colonic epithelial cells. These cells are constantly reproducing in a regulated manner, but when the growth and division of colonic epithelial cells becomes unregulated, colon cancer may result.
Cancer is a form of unregulated cell growth in which growing cells invade surrounding tissue. Such a growth is said to be malignant. Colon cancer results when there are certain changes in the genes that control normal cell replication. In most cases, when cell growth becomes abnormal, a visible growth (lesion) protrudes into the colon's lumen and is termed an adenomatous polyp (or adenoma). The polyp is not yet cancerous but may become so, at which point it is called carcinoma. This process, in which normal tissue becomes cancerous, is known as the adenoma-carcinoma sequence and may take between ten and fifteen years.
Medicine EncyclopediaGenetics in Medicine - Part 1Colon Cancer - Developing Cancer, Major Genes Involved, Familial Adenomatous Polyposis (fap), Hereditary Nonpolyposis Colon Cancer - Other Risk Factors