Colorectal cancer (CRC) is a common cancer of the colon or rectum. CRC is characterized by tumor growth that starts on the inner lining (mucosa) of the intestines. Advanced CRC can also affect other parts of the body, including the liver and lungs.
CRC results from abnormal cell growth in the mucosa forming a polyp, which is a small, benign (precancerous) bump. If left untreated, polyps can grow larger to become cancerous tumors. Large CRC tumors cause bowel obstruction and often require surgery.
In advanced CRC, the cancer can metastasize (spread) through lymph and blood vessels to other areas of the body. The most common site of CRC metastasis is the liver, connected to the intestines by the hepatic portal vein system. CRC can also spread to the lungs via the inferior vena cava (a large vein in the abdomen), forming cannonball-shaped masses.