All About Colon Polyps

Key Takeaways

• A colon polyp is a mass of tissue on the inside wall of the colon that protrudes into the colon "tube."
• Most colon cancers arise from a polyp; however, only a very small percentage of colon polyps become cancer.
• Polyps can be grouped into those that do NOT become cancer (non-neoplastic polyps) and those that CAN become cancer (neoplastic polyps).
• Polyps can be found with colon cancer screening tests, including colonoscopy.
• Removing polyps that can become cancer lowers the risk of colon cancer by up to 80%.

What is the colon?

The colon is a tube that is about 5 to 6 feet long that connects to about 6 inches of rectum, and finally ends with the anus. The exact length of the colon depends on the person. The colon and rectum make up the last part of the digestive tract. The digestive tract includes the mouth, esophagus, stomach, small bowel, and large bowel.
The colon has several parts (in the order that stool travels through): the cecum and ascending colon (on the right side), the transverse colon (goes across the abdomen/belly), the descending colon (on the left side), and the sigmoid colon. The cecum connects to the small intestine, while the sigmoid colon connects to the rectum. The colon's job is to change liquid waste into solid stool. The stool can spend 10 hours to many days in the colon before exiting through the anus.

What is a colon polyp?

A colon polyp is a mass of tissue on the inside wall of the colon that protrudes into the colon "tube." Colonic polyps are common. They are found in more than 25% of people over the age of 60.

Polyps usually do not cause any symptoms. They can cause bleeding. If they are very large and have become cancer, they can block stool in your bowel (obstruction). Sometimes you can see the blood in your stool. In some cases, it is occult (meaning you cannot see it) and can lead to iron-deficiency anemia (low red blood cell counts). Intestinal obstruction can cause nausea, vomiting, abdominal distension (bloating), and severe belly pain. If an obstruction is not treated, it can lead to perforation, or tearing of the wall of the colon. This needs to be treated right away and is a very serious issue.

What causes colon polyps?

Colon polyps develop due to a combination of environmental and genetic factors. Some factors thought to increase the risk of colon polyps include high-fat diet, a diet high in red meat, and likely, tobacco, smoking, and obesity. Polyps are more common as you age. Polyps and colon cancer in family members can increase your risk and this history should be discussed with your healthcare providers.

How are polyps diagnosed?

Many tests are used to find polyps. The test most often used is colonoscopy.

Learn more about the tests available for colon cancer screening.

How are polyps related to colon cancer?

Most colon cancers start as a polyp but only a very small number of colon polyps become cancer. You should know the different types of polyps and the risk factors that increase the chance that they will become cancer.

Polyps can be grouped into those that do NOT become cancer (non-neoplastic polyps) and those that CAN become cancer (neoplastic polyps). There are ways that the gastroenterologist can decide if a polyp is neoplastic or non-neoplastic and if it needs to be biopsied.

What are the different kinds of polyps?

Polyps are either neoplastic (adenoma), meaning they have the potential to become cancer, or non-neoplastic (hyperplastic), meaning they will not become cancer. They can also be described by their shape: sessile (flat), pedunculated (having a stalk), and flat or "depressed.”

Non-Neoplastic Polyps

Non-neoplastic polyps do not become cancer. They are many reasons you could have one of these polyps. There are many types of non-neoplastic polyps: 

• Hyperplastic polyps make up most colon polyps. These are often in the non-neoplastic category. Some patients with these polyps have hyperplastic polyposis syndrome, making them more at risk for polyps. This rare syndrome is defined by the number of hyperplastic polyps, their size, and where they are found. 
• Inflammatory pseudopolyps are not really polyps. They are formed when ulcers in the colon heal, leaving the mucosa (lining of the colon) to look like a polyp. There can be one or many and they can be very large. Inflammatory pseudopolyps can develop in any form of severe colitis, including Crohn's disease, ulcerative colitis, and ischemic colitis. 

Neoplastic Polyps

Neoplastic polyps can lead to cancer. Neoplastic polyps can lead to a type of cancer called "carcinoma." These polyps look different than other polyps under a microscope.

• Adenomatous polyps can lead to invasive colon and rectal cancer. They are grouped into villous, tubulovillous, and tubular adenoma subtypes by how they look under. Villous polyps are the most likely to progress to cancer, followed by tubulovillous and finally, tubular polyps.
  • About 10-30% of adenomas are familial, meaning they happen due to genetic variations. Other risk factors for adenoma are increasing age and perhaps, a high-fat diet. Adenomas should be removed since they can lead to cancer.
• Carcinomatous polyps are a type of adenoma and contain cancer. Malignant polyps make up about 5% of adenomas and are also often removed. However, they are more likely to lead to cancer or to spread to lymph nodes. Malignant polyps should be removed when certain high-risk factors are found, such as invasion of blood vessels or lymphatics, invasion of deeper tissues, involvement of polypectomy margin with cancer, and poor degree of differentiation.
• Serrated polyps may be sessile or pedunculated. There is research that serrated polyps are a part of a distinct pathway that can lead to cancer. Three distinct types of serrated polyps have been found, including hyperplastic polyp, sessile serrated adenoma (SSA), and traditional serrated adenoma (TSA).
  • Hyperplastic polyps (see above) are small sessile lesions and are often less than 5 mm. Hyperplastic polyps are common but are not precursors to cancer.
  • SSAs and TSAs have features of both hyperplastic polyps and adenomatous polyps. SSAs and TSAs are much rarer than hyperplastic polyps. These polyps lead to cancer. They are often treated like adenomas.

What are "polyposis syndromes?"

Polyposis syndromes are conditions that cause many polyps. They are often caused by a genetic abnormality within a family. Most lead to an increased risk of colon cancer, as well as pancreatic, thyroid, and breast cancer.

Familial adenomatous polyposis (FAP) 

FAP is the most common polyposis syndrome and is a result of a change in the APC gene. People with FAP have hundreds to thousands of adenomatous polyps in their large intestine. Polyps are also found in the stomach and small intestine. FAP results from a mutation in the APC (adenomatous polyposis coli) gene. All types of adenomatous polyps can be seen, including tubular, villous, and tubulovillous. It is diagnosed when at least 100 adenomas are found during a colonoscopy. Those with a family member with FAP should have genetic testing at 10-12 years of age. If untreated, 100% of people with FAP will develop colon cancer, often before 40 years of age. To treat FAP, surgery is done to remove the colon. In some cases, a total abdominal proctocolectomy is done, which removes the entire colon and rectum with ileo-anal anastomosis (J-pouch). People with FAP are also at more of a risk for cancer of the duodenum (first part of the small intestine), stomach, pancreas, thyroid, liver, bone, and brain. They are also at risk for intra-abdominal growths called desmoid tumors.

Turcot’s Syndrome

Turcot's syndrome also results from changes to the APC gene and is characterized by colonic polyposis and a rare type of brain tumor. Family members of those affected should have a screening colonoscopy along with imaging of the brain (eg. MRI). Turcot's may be similar to Lynch syndrome or FAP, and will help determine the exact risks.

Gardner’s Syndrome

Gardner's syndrome also results from APC mutations and is characterized by colonic polyposis, osteomas (benign bone tumors), dental abnormalities, and a variety of other benign tumors. Osteomas most commonly affect the mandible (the jawbone). They are only removed to improve symptoms or cosmetic appearance since they are benign. People with Gardner's Syndrome have a similar risk of colorectal cancer as those with FAP. They should talk to a genetic specialist about screening.

Peutz-Jeghers Syndrome

Peutz-Jeghers syndrome is characterized by a change in color around the mouth, nose, lips, hands, and feet, along with polyps of the stomach, small intestine, and colon. It is caused by a change in the STK1 (LKB1) gene. The polyps are found mostly in the small intestine but can be found in the colon. Patients should have a colonoscopy at least every 2-3 years when symptoms start or starting in the late teens (if asymptomatic), as well as a small bowel investigation every 1-3 years depending if there are polyps. This is done with diagnostic capsule endoscopy, and as needed, small bowel endoscopy. Polypectomy is used for treatment, while surgery is used for large, hard to remove or recurrent polyps. People with Peutz-Jeghers syndrome are also at higher risk of cancer of the small intestine, pancreas, breast, uterus, ovaries, lung, cervix, or testes. 

Juvenile Polyposis Syndrome

Juvenile polyposis consists of many benign hamartomatous (juvenile) polyps in the colon and rectum. It affects the PTEN, BMPR1A, or SMAD4 genes. They often cause bleeding, intussusception, or bowel obstruction. Intussusception is a condition where the intestine folds in on itself like a telescope, causing abdominal pain, nausea, vomiting, and blood in the stools. There is a higher risk for cancers of the colon, small intestine, and possibly stomach. Colonoscopy should be done at least every 3 years, when symptoms begin, or in the early teens (if asymptomatic). Juvenile polyps should be removed by polypectomy. Colectomy (removal of the colon) can be done if there are many polyps. 

Lynch Syndrome (HNPCC or Hereditary Non-Polyposis Colorectal Cancer)

Lynch syndrome can lead to colon cancer, breast, gastric, and ovarian cancers. Women with Lynch syndrome are also at higher risk to develop endometrial cancer (cancer of the uterus). breast, gastric, and ovarian cancers.

There are other polyposis syndromes including Bloom's syndrome, familial tooth agenesis syndrome, MUTYH polyposis, PTEN hamartoma tumor syndromes, neurofibromatosis, Cronkhite-Canada syndrome, hyperplastic polyposis syndrome, and nodular lymphoid hyperplasia. Refer to the resources below for further information.

How are polyps treated? What follow-up do I need?

Polyps are treated by removal (polypectomy) during colonoscopy using electrocautery. This means they are cut out and the tissue is burned to seal off the tissue and blood vessels and stop any bleeding. If the polyps were detected with a screening test other than colonoscopy, you will need to have a colonoscopy to remove the polyps

Small polyps can be removed entirely by biopsy. Bleeding is the most common side effect. Other less common but serious side effects include bowel perforation and electrocautery burn. These can be serious and may require surgical repair. The goal of polypectomy is to remove the entire polyp. When one polyp is found, it is important to examine the entire colon to look for additional polyps.

Polyps can also be treated surgically when they can’t be removed during a colonoscopy or for patients with polyposis syndromes that need further treatment. Surgery for polyps and polyposis syndromes should be done by a colorectal surgeon.

Removing adenomas greatly lowers the risk of developing colon cancer. Based on the National Polyp Study, polypectomy reduces the risk of colon cancer up to 80%. However, the number, size, and location of the adenomas affect the colon cancer risk. Adenomas can come back after they are removed. People with a history of neoplastic polyps may have a higher risk of colon cancer compared to the average population. It is recommended that they have screening colonoscopies more often. Once a person has their first screening colonoscopy, further follow up is recommended based on the findings of that first test.

The U.S. Multi-Society Task Force on Colorectal Cancer has the following recommendations for colonoscopy follow up:

Talk to your provider about any questions you may have about polyps or colonoscopies. 

Resourced for More Information

Genetic Testing For Familial Colorectal Cancer 

Familial Colorectal Cancers: Hereditary Non-Polyposis Colon Cancer (HNPCC)

Familial Colorectal Cancers: Familial Adenomatous Polyposis (FAP)