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The causes of rectal cancer aren’t yet fully understood, but research has provided some insight into how and why these cancers develop. Almost all rectal cancers first develop as small, slightly raised growths on the inner surface of the rectum; these are known as polyps. While healthy cells die off after their regular life span is complete, abnormal cells with damaged DNA can divide rapidly and create polyps as they reproduce without restraint.  

Not all polyps become cancerous. Studies show that certain types of polyps are more likely to become cancerous than others; for instance:

  • Hyperplastic polyps very rarely develop into rectal cancer.
  • Adenomatous polyps have a greater potential to become cancerous.
  • Serrated polyps can also become cancerous, but this occurs much less frequently than with hyperplastic or adenomatous polyps.

Polyps that become cancerous do so at different rates depending on their size and cellular makeup. For instance, studies show that polyps that are larger than 1 centimeter when they are discovered are more likely to become malignant than polyps that are smaller when detected. However, researchers have not yet conclusively determined what causes some polyps to transform into cancerous tumors while others do not. 

Inherited gene mutations that increase the risk of colon and rectal cancer

Some gene mutations that pass from parents to their children can increase the risk of developing colorectal cancers; however, these mutations have only been associated with a small percentage of rectal cancers. Two genetic syndromes associated with colorectal cancers are Lynch syndrome and familial adenomatous polyposis. These and other syndromes associated with colorectal cancers can be detected through genetic testing.

Research at Moffitt Cancer Center

At Moffitt Cancer Center, our dedicated researchers are continually working to better understand the causes of rectal cancer. As a National Cancer Institute-designated Comprehensive Cancer Center, we have been recognized for our scientific leadership and laboratory breakthroughs; more importantly, we have a unique system to immediately use these breakthroughs for our patients’ benefit. Because our oncologists go directly from bench to bedside – meaning that they are involved with our scientific research throughout the course of their careers – we’re able to promptly apply what we learn in the lab to what we offer our patients.

If you’d like to learn more about the causes of rectal cancer, you can schedule an appointment with one of our oncologists with or without a referral. To do so, call 1-888-663-3488 or submit a new patient registration form online.