Learning about CRC

How colorectal cancer develops

Colon and rectal cancers are alike in many ways, which is why we sometimes refer to them together as colorectal cancer. Symptoms and treatment can vary according to where the cancer grows, so it might be helpful for you to know more about the colon and rectum.

The colon and rectum are part of the digestive system (sometimes called the gastrointestinal or GI tract). The digestive system processes the food we eat and eliminates solid waste matter (feces or stool) from the body.

Diagram of the digestive system

The digestive system consists of the esophagus,
stomach, and the small and large intestines.

Where they grow

Colorectal cancers develop in the large intestine. The first 6 feet of the large intestine include the large bowel or colon. The final 6 inches make up the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body). The colon has 4 sections: the ascending colon, the transverse colon, the descending colon, and the sigmoid or S-shaped colon. Cancer can develop in any of the 4 sections of the colon or rectum.

How they grow

Colorectal cancers usually begin as a small clump of benign cells (called a polyp) that start to grow in the inner wall of the colon and rectum. Over time, some polyps can become cancerous. As the cancer grows, it can spread through the wall to nearby tissue outside the colon or rectum. Eventually, cancer cells may break away and spread to other parts of the body, where they form new tumors. This spreading process is called metastasis, and the new tumors are called metastases.

Next: Diagnosis of Colorectal Cancer