Your doctor can't usually tell, simply by looking at a polyp during a colonoscopy, if it's cancerous. But if a polyp is found during your colonoscopy, your doctor will remove it and send it to a lab for a biopsy to check for cancerous or precancerous cells.
Cancerous tissues
A colonoscopy test is also effective in detecting cancerous tissue. While cancer often starts in polyps, it can also form in abnormal cells, called dysplasia, in the lining of the rectum or colon. As cancer grows, it can spread to the wall of the colon and rectum.
Most polyps are benign (not cancerous). Your doctor can tell if a colon polyp is cancerous during a colonoscopy by collecting tissue to biopsy. The results of the biopsy are typically sent to your doctor within a week.
Screening finds precancerous growths on the colon wall, called polyps, which the doctor can then remove. They are not cancer, and most of them have not started to change into cancer. If you get them at the precancerous phase, they don't have a chance to grow and turn into cancer.
“Less than 1% of colonoscopies result in a finding of cancer,” says Uppal. “But even if yours is one of them, no one is going to perform an unplanned procedure on you while you're sedated. Sometimes, we might have to stop the colonoscopy because there's too much stool present for us to see things clearly.
If the cancer has not spread then the doctor may suggest removing the cancerous polyps, usually through either a colonoscopy or laparoscopy. However, often the cancer has spread to the muscles surrounding the colon. In this instance, the doctor may opt for a colectomy.
Here's what we know: As often as 40% of the time, a precancerous polyp — frequently a type called an adenoma — is found during a screening colonoscopy. Colon cancer is found during only in about 40 out of 10,000 screening colonoscopies, Dr. Sand said.
Right-sided polyps are more likely to develop into cancers — which often grow rapidly and have a higher risk for metastasis, spreading to distant body areas.
Colon polyps are small growths on the lining of the large intestine (colon). They're usually benign, meaning they won't cause any problems, especially at early stages. However, when they start growing too fast or larger than usual, they could turn into cancer.
But only removal for examination under a microscope by a pathologist can accurately determine if a polyp is precancerous.
Colon polyps can appear in a number of ways: Pedunculated: A little ball of tissue on the end of a stalk, like a broccoli floret or a mushroom. Sessile: A smooth bump or a gradually sloping “hill” on the lining of the colon. Flat: These are often very hard to see, as they may have no visibly raised portion at all.
Ninety percent of cases occur after age 50, with males somewhat more likely to develop polyps than females; therefore, colon cancer screening is usually recommended starting at age 50 for both sexes. It takes approximately 10 years for a small polyp to develop into cancer.
Usually if a suspected colorectal cancer is found by any screening or diagnostic test, it is biopsied during a colonoscopy. In a biopsy, the doctor removes a small piece of tissue with a special instrument passed through the scope. Less often, part of the colon may need to be surgically removed to make the diagnosis.
If your doctor finds one or two polyps less than 0.4 inch (1 centimeter) in diameter, he or she may recommend a repeat colonoscopy in 7 to 10 years, depending on your other risk factors for colon cancer. Your doctor will recommend another colonoscopy sooner if you have: More than two polyps.
You should get a letter or a call with your results 2 to 3 weeks after a colonoscopy. If a GP sent you for the test, they should also get a copy of your results. Call the hospital if you have not heard anything after 3 weeks.
They can occur anywhere in the large intestine or rectum, but are more commonly found in the left colon, sigmoid colon, or rectum.
Colorectal cancer is preventable. Nearly all cases of colorectal cancer develop from polyps. They start in the inner lining of the colon and most often affect the left side of the colon and rectum.
In most cases, no. Your doctor can't usually tell, simply by looking at a polyp during a colonoscopy, if it's cancerous. But if a polyp is found during your colonoscopy, your doctor will remove it and send it to a lab for a biopsy to check for cancerous or precancerous cells.
Approximately 1% of polyps with a diameter less than 1 centimeter (cm) are cancerous. More than one polyp or a polyp that is 1 cm or bigger places you at higher risk for colon cancer. Up to 50% of polyps greater than 2 cm (about the diameter of a nickel) are cancerous.
Most colorectal cancers start as a growth on the inner lining of the colon or rectum. These growths are called polyps. Some types of polyps can change into cancer over time (usually many years), but not all polyps become cancer. The chance of a polyp turning into cancer depends on the type of polyp it is.
Cancerous polyps tend to grow slowly. It is estimated that the polyp dwell time, the time needed for a small adenoma to transform into a cancer, may be on average 10 years (17).
In most cases this can be done by removing the polyp or taking out the area with cancer through a colonoscope (local excision). Removing part of the colon (partial colectomy) may be needed if a cancer is too big to be removed by local excision.
Colon cancer, or cancer that begins in the lower part of the digestive tract, usually forms from a collection of benign (noncancerous) cells called an adenomatous polyp. Most of these polyps will not become malignant (cancerous), but some can slowly turn into cancer over the course of about 10-15 years.