Colon polyps

Overview

A colon polyp is a small clump of cells that forms on the lining of the colon. Most colon polyps are harmless. But over time, some colon polyps can turn into colorectal cancer. Colorectal cancer can be deadly when found in its later stages.

The most common type of precancerous polyp is an adenomatous polyp, often called an adenoma. Because adenomas are the polyps that most often change into colorectal cancer, healthcare professionals recommend removing them to prevent them from growing larger or becoming cancerous.

Anyone can develop colon polyps, and your risk increases as you age. Your risk of colorectal cancer also is higher if you are overweight, smoke, have a personal history of colon polyps, or have a family history of advanced colon polyps or colorectal cancer.

Colon polyps don't usually cause symptoms. It's important to have regular screening tests because colon polyps found early can usually be taken out safely and completely. The best prevention for colorectal cancer is regular screening.

Types

Medical professionals classify colon polyps into two groups, nonneoplastic and neoplastic. Nonneoplastic polyps are generally harmless and rarely turn into cancer. Neoplastic polyps are considered precancerous, which means they can turn into cancer if they are not taken out.

Noncancerous polyps

Nonneoplastic polyps are generally considered harmless. They include:

• Hyperplastic polyps. These are very common, especially in the lower colon and rectum. They are usually small and almost never turn into cancer.
• Inflammatory polyps. These polyps often occur in people with inflammatory bowel disease such as Crohn's disease or ulcerative colitis. These polyps also are called pseudopolyps. The polyps themselves do not turn into cancer, but they indicate long-term inflammation in the colon, which raises overall cancer risk.
• Hamartomatous polyps. These polyps are made of regular tissue that grows in a way that's not organized. In a child, a single polyp is usually harmless and often goes away on its own. However, when many are present, as in juvenile polyposis syndrome, cancer risk increases. Peutz-Jeghers polyps are another type that appear in a rare genetic syndrome and are linked to higher cancer risk. PTEN-hamartoma polyps, seen in Cowden syndrome, also can raise cancer risk.

Precancerous polyps

Neoplastic polyps are more likely to become cancerous. They include:

• Adenomas, also called adenomatous polyps. These are the most common neoplastic polyps. They include:
  • Tubular adenomas. These are the most common type and usually have the lowest risk of becoming cancer.
  • Tubulovillous adenomas. These polyps combine features of tubular and villous adenomas and carry a higher risk.
  • Villous adenomas. These are the least common but the most likely to turn into cancer, especially when large.
• Serrated polyps. These polyps follow a distinct pathway to cancer. They include:
  • Sessile serrated lesions (SSLs). SSLs are flat polyps often found in the right colon. They can be difficult to detect during colonoscopy and may change into cancer, especially if they are large or show irregular cell growth. SSLs are sometimes called sessile serrated polyps (SSPs) or sessile serrated adenomas (SSAs).
  • Traditional serrated adenomas (TSAs). TSAs are rare and usually located in the left colon. These are clearly precancerous and are always removed when found.

Symptoms

Most people with colon polyps do not have any symptoms, which is why screening tests are so important. Colon polyps are often found as a part of routine colorectal cancer screening.

Symptoms that should prompt an appointment with a healthcare professional include:

• Changes in bowel habits. Constipation or diarrhea that lasts longer than a week may mean the presence of a larger colon polyp or cancer. However, several other conditions also can cause changes in bowel habits.
• Changes in stool color. Blood can show up as red streaks in the stool or make stool appear black. A change in color also may be caused by certain foods, medicines or dietary supplements.
• Mucus in stool. Stool often contains a small amount of mucus. Mucus is a jellylike substance that your intestines make to keep the lining of your colon moist and lubricated. But you should talk with a healthcare professional if you notice an increased amount of mucus in stool. Mucus by itself usually isn't a reason to do medical tests, but it's helpful to know if you see it along with other symptoms.
• Iron deficiency anemia. Bleeding from polyps can happen slowly over time, without visible blood in the stool. Chronic bleeding may lead to iron deficiency anemia, which can cause tiredness and shortness of breath.
• Pain. A large colon polyp or cancer can block part of the bowel, leading to cramping and belly pain.
• Rectal bleeding. This can be a sign of colon polyps, cancer or other conditions, such as hemorrhoids or minor tears of the anus.

When to see a doctor

See a healthcare professional if you have:

• Belly pain.
• Blood in the stool.
• A change in bowel habits that lasts longer than a week.
• Weight loss that happens without trying.

You should be screened regularly for colorectal cancer if:

• You're age 45 or older.
• You're younger than age 45 and you have medical conditions or family history that increases your risk of colorectal cancer.

Causes

Experts haven't found a single cause for colon polyps. They form when the usual process of cell growth and repair in the colon goes off track. Instead of replacing old cells in an orderly way, the body makes extra cells, which build up and form a polyp on the smooth lining of the intestine. Polyps can grow anywhere in the large intestine, including in the colon and rectum.

When polyps grow in the rectum, they are called rectal polyps. The rectum is the lower part of the colon, so rectal polyps are simply a type of colon polyp.

Aside from being classified by where they grow, colon polyps also are classified by their type. Noncancerous, also called nonneoplastic, polyps usually do not become cancer. Precancerous, also called neoplastic, polyps include adenomas and serrated lesions. Most colorectal cancers begin in an adenoma or serrated lesion that has been present for many years. In general, the larger the precancerous polyp, the greater the risk that it will become cancerous.

Risk factors

Factors that might increase the risk of colon polyps or cancer include:

• Age. Most people with colon polyps are 45 or older.
• Having certain intestinal conditions. Having inflammatory bowel disease, such as ulcerative colitis or Crohn's disease, raises the overall risk of colorectal cancer.
• Family history. Having a parent, sibling or child with advanced colon polyps increases the risk of getting them. An example of an advanced colon polyp is one that is 10 mm in diameter or larger. If many family members have them, the risk is even greater.
• Personal history of colorectal polyps. Previous polyps are a risk factor for forming new polyps.
• Smoking and excess alcohol use. Studies show that people who have three or more alcoholic drinks a day have an increased risk of getting colon polyps. Alcohol intake combined with smoking also appears to increase the risk.
• Having diabetes. Diabetes increases polyp risk by 50% among all age groups.
• Obesity, lack of exercise and a less healthy diet. The risk of colon polyps increases for people who are overweight, don't exercise regularly and eat a less healthy diet.
• Race. In the U.S., Black people have a higher risk of developing colorectal cancer.

Polyp syndromes

Hereditary conditions are health concerns passed down from parents. Rarely, people inherit gene changes that cause colon polyps to form and increase the risk of colorectal cancer. Screening and early detection can help prevent the growth or spread of these cancers.

Conditions that cause colon polyps include:

• Lynch syndrome, also called hereditary nonpolyposis colorectal cancer. People with Lynch syndrome may have relatively few colon polyps, but those polyps can quickly become cancerous. Lynch syndrome is the most common inherited form of increased colon cancer risk and also is associated with cancers in other parts of the body, including the skin, stomach, uterus and bladder.

  If multiple members of a family have these cancers, especially if any one of them had them at an age younger than 50 years, it could be a sign that the family has a Lynch syndrome gene. Cancer risks are substantially lessened in people with Lynch syndrome who follow up regularly with their healthcare professionals for screening tests.

• Familial adenomatous polyposis (FAP), a rare condition that results in hundreds or even thousands of polyps in the lining of the colon in teenagers or young adults. If the polyps aren't treated, the risk of developing colon cancer is nearly 100%, usually before age 40. The risks are lessened through regular colon cancer screening tests as well as surgery to remove the affected colon, called colectomy. Genetic testing can help determine the risk of FAP.
• MUTYH-associated polyposis (MAP), a condition similar to FAP that is caused by changes in the MUTYH gene. People with MAP often develop multiple adenomatous polyps and colon cancer at a young age. Genetic testing can help determine the risk of MAP.
• Peutz-Jeghers syndrome, a condition that usually begins with freckles developing all over the body, including the lips, gums and feet. Then noncancerous polyps develop throughout the intestines. These polyps may become cancerous, so people with this condition have a higher risk of colon cancer.
• Juvenile polyposis syndrome (JPS), an inherited condition that is most common in children ages 1 to 7, though it sometimes happens in adults. Juvenile polyps are often single, but if there are multiple polyps, the risk of cancer is higher.
• Serrated polyposis syndrome is most often a condition that is not inherited but defined based on polyp history. People with multiple serrated lesions may have this syndrome. Because these polyps may become cancerous, they need to be taken out. People with this syndrome have colonoscopies more often.

Complications

Some colon polyps may become cancerous. The earlier polyps are taken out, the less likely it is that they will become cancerous.

Prevention

The risk of colon polyps and colorectal cancer may be greatly reduced by having regular screenings. Certain lifestyle changes also can help:

• Adopt healthy habits. Include plenty of fruits, vegetables and whole grains in your diet and reduce your fat intake. Limit alcohol and quit all tobacco use. Stay physically active and keep a healthy body weight.
• Consider your options if you're at high risk. If you have a family history of colon polyps, talk with a healthcare professional. If you have a personal history of 10 or more neoplastic polyps, consider having genetic counseling. Referral to a genetic counselor also may be considered depending on your family history. If you've been diagnosed with a hereditary disorder that causes colon polyps, you'll usually need regular colonoscopies starting in young adulthood.