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. Only 5% to 10% of all polyps become cancerous.
A gastroenterologist, the specialist who usually performs a colonoscopy, can't tell for certain if a colon polyp is precancerous or cancerous until it's removed and examined under a microscope.
Colon Cancer Diagnosis: Getting a Colonoscopy
Screening is crucial for cancer detection because most colorectal cancers don't cause symptoms in the early stages. Many times, doctors first spot colon cancer during a routine screening colonoscopy.
Some types of colon polyps are more likely to become cancerous than others. A doctor who specializes in analyzing tissue samples (pathologist) will examine your polyp tissue under a microscope to determine whether it is potentially cancerous.
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.
Adenomas: Many colon polyps are the precancerous type, called adenomas. It can take seven to 10 or more years for an adenoma to evolve into cancer—if it ever does. Overall, only 5% of adenomas progress to cancer, but your individual risk is hard to predict.
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). Evidence from the heyday of barium enema examinations indicates that most polyps do not grow or grow very slowly (18).
If they found precancerous cells, there is no need for any additional treatment as long as they removed the entire polyp. Removing the tissue stops the development of cancer. Since you are still at an increased risk, we will likely recommend repeating the screening every three to five years in the future.
Most polyps are protrusions from the lining of the intestine: Polypoid polyps look like a mushroom, but flop around inside the intestine because they are attached to the lining of the colon by a thin stalk. Sessile polyps do not have a stalk, and are attached to the lining by a broad base.
Polyps are common in American adults, and while many colon polyps are harmless, over time, some polyps could develop into colon cancer. While the majority of colon cancers start as polyps, only 5-10% of all polyps will become cancerous.
Approximately 6% of colorectal cancers are diagnosed within 3 to 5 years after the patient received a colonoscopy, according to findings from a recent population-based study.
However, it will take some time to receive your test results from the lab that will confirm or rule out cancer. Your doctor may have some information for you prior to the lab test results, but the official results will come from the lab within a couple weeks.
Colonoscopy Isn't Perfect: About 6% of Colorectal Cancers Are Missed | University of Utah Health.
Although any neoplasms were detected in more than 20% of participants even at colonoscopies conducted within five years of a negative colonoscopy, detection of advanced neoplasms within 10 years was rare.
If a polyp has cancerous cells, they will also biopsy nearby lymph nodes to determine if the cancer has spread or metastasized to other areas of the body. In this case radiation, chemotherapy or other therapies may be recommended. Colonoscopy screenings can be life saving!
They can occur anywhere in the large intestine or rectum, but are more commonly found in the left colon, sigmoid colon, or rectum.
A polyp is a small growth of excess tissue that often grows on the lining of the large intestine, also known as the colon. Colon and rectal polyps occur in about 25 percent of men and women ages 50 and older. Not all polyps will turn into cancer, and it may take many years for a polyp to become cancerous.
They may feel your stomach area (abdomen) to see if there are any lumps or tender areas. They may also do a digital rectal examination (DRE). This involves putting a gloved finger inside the back passage (anus) to feel for any lumps. This can be uncomfortable but it shouldn't be painful and it is over quickly.
Colonoscopies can detect conditions like colitis, inflammatory bowel disease and diverticulosis. But mainly, doctors are looking for precancerous or cancerous colon polyps, which are growths on the inside of the colon's lining.
If your doctor thinks an area needs further evaluation, he or she might pass an instrument through the colonoscope to obtain a biopsy (a small sample of the colon lining) to be analyzed. Biopsies are used to identify many conditions, and your doctor will often take a biopsy even if he or she doesn't suspect cancer.
If a cancerous polyp is removed completely during colonoscopy with no cancer cells at the edges of the polyp, then no additional treatment may be needed. If there are cancer cells at the edges of the polyp, additional surgery may be needed.
Larger polyps might be removed during colonoscopy using special tools to remove the polyp and a small amount of the inner lining of the colon in a procedure called an endoscopic mucosal resection. Minimally invasive surgery (laparoscopic surgery).
Most colorectal cancers start as polyps, however, not all polyps turn into cancer. A doctor will often remove polyps once they are detected, usually during a colonoscopy. They will usually send these polyps off for a biopsy to test them for cancer.
However, over time polyps can become large and malignant if they aren't treated. Many polyps are found to be pre-cancerous, which means they have the potential to turn cancerous if they aren't removed. With early detection through an endoscopic test, the risk can be eliminated by your gastroenterologist.