What Is Colon and Rectal Cancer (Colorectal Cancer)?

Cancer starts when cells in the body change (mutate) and grow out of control. These cells can form lumps of tissue called tumors. Cancer that starts in the cells of the colon is called colon cancer. Cancer that starts in the cells that make up the rectum is called rectal cancer. These cancers are a lot alike, so they're sometimes just called colorectal cancer.