Common after the age of 40, they appear as irregularities in the mucous membrane, i.e. the wall of the colon or rectum. However, the polyps are not all the same: they vary in shape, size and growth pattern. Although not all polyps become tumors, all neoplasms start as polyps. It is therefore important to characterize them during colonoscopy and above all to remove those that have this degenerative potential. Let’s see together with Dr. Milena Di Leo which polyps exist and which are more likely to lead to colorectal cancer.
Types of polyps and meanings
The endoscopes currently available in many centers, thanks to their excellent resolution and the aid of coloring, help us to identify polyps and also to predict their type. Despite these improvements, the certain method to diagnose the type of polyp is its evaluation under the microscope: they must then be removed (partially or completely) and analyzed histologically.
Colorectal polyps can be classified by form. About 85% of polyps are “sessile”, i.e. they have the shape of a dome, without stem. On the other hand, 13% are “pedunculate”, like a fungus hanging on the wall of the colon. Finally, about 2% of precancerous lesions are completely flat.
The shape influences the ease with which the polyps can be visualized by the endoscopist: the pedunculated polyp is generally well visible, while the flat polyp is more complex to identify because it is so thin that it tends to blend with the parts of the colon-rectum and often even minimal residues of feces can make it difficult to visualize. This explains the importance of a good intestinal preparation: it allows carrying out a very accurate colonoscopy, to visualize and remove all the observed polyps so as not to have to repeat the exam in a short time.
Why is the size of a polyp so important?
Polyps can be less than 5 millimeters in size but can also reach over 30 millimeters. The smaller the polyp, the less likely it is to be malignant: those larger than 20 millimeters in fact have 10% more chance of having cells modified within them. Degenerated cells have different degrees of “modification” from mild dysplasia to tumor. Under the microscope, these different stages are identified and these cells seem larger and disorganized with larger and darker nuclei than healthy cells.
The size, together with the shape of the polyp, also changes the type of removal: in general, pedunculate polyps can be removed in one piece, while sessile polyps, especially larger ones, may require removal in several fragments or a procedure in hospital.
Conventional adenoma and serrated polyps: what is the difference?
In recent years, there is ample evidence that the development of colorectal cancer can also occur from a different type of adenoma, namely the serrated sessile polyp.
75% of colon tumors come from polyps called conventional adenomas (which may be tubular or villous), derived from glandular cells in the colon.
On the other hand, 25% of the tumors come from serrated polyps. These are usually thin, light-colored, unshaped, serrated mucous membranes of the colon, covered with a thin layer of mucus. These characteristics make them less visible during colonoscopy.
Symptoms that should not be underestimated
“Colorectal polyps do not have specific symptoms – said the doctor. They grow lazy for years and show signs of their presence when they become large or when they have degenerated into cancer. And that is why over 50 years of age is recommended to perform a colonoscopy: in fact, the endoscopic examination is the only test that can identify and remove the polyps of the colon-rectum. It is an invasive examination, but today, with the help of painkillers and sedatives, it is conducted without particular discomfort to the patient.
The age of execution of the first colonoscopy can be anticipated if there is a relative who has had a tumor of the rectum. Given the need to collect further information, in these cases a specialist gastroenterological examination is necessary to establish the right time for the examination and any request for further investigation.
