Colorectal cancer causes are largely unknown. Medical experts have determined that cancer can develop in the lining of the colon or rectum when healthy cells undergo changes that cause them to accumulate into masses, or polyps. However, the reasons those changes occur remain unclear. While some types of polyps are benign, others (adenomatous polyps or adenomas) are cancerous. Adenomas can potentially penetrate the colon wall and invade blood vessels, lymph nodes and distant tissues and organs.
There is some evidence that certain inherited gene mutations can increase the risk of cancers of the colon and rectum. For instance, some forms of colorectal cancer, and their underlying causes, have been associated with family history. Those include:
- Familial adenomatous polyposis (FAP) – This rare condition triggers the development of thousands of polyps in the lining of the colon and rectum. Left untreated, FAP can significantly increase the risk of developing colorectal cancer before age 40.
- Hereditary nonpolyposis colorectal cancer (HNPCC) – Also known as Lynch syndrome, HNPCC increases the risk of developing colorectal cancer prior to age 50.
- Juvenile polyposis (JP) – Before age 10, up to 500 polyps form in the colon and rectum. JP can increase the risk of both colorectal and bowel cancers.
- Peutz-Jehgers syndrome (PJS) – Thousands of polyps grow in the stomach, intestines, colon and rectum. These growths can potentially become malignant or obstruct the bowel.
It is important to note that inherited gene mutations have been linked to only a small percentage of colon cancer cases, and therefore are not considered to be definitive colorectal cancer causes. Nevertheless, individuals who have a family history of colorectal cancer are encouraged to consult with the experts at Moffitt Cancer Center, who can provide an in-depth risk assessment. For some patients, our multispecialty tumor board may recommend genetic testing, which can detect certain inherited colorectal cancer syndromes.