Polyp types in plain English
In short
Polyps are sorted into types under the microscope. The three you are most likely to read about on a pathology report are hyperplastic polyps, adenomas, and sessile serrated lesions. Each carries a different relationship to colorectal cancer risk, and each is the reason the report contains the recommendations it does.
What this page covers
The main families of colon polyp, what each one is made of, the words your pathology report tends to use to describe them, and what the type means in practical terms for follow-up.
- Hyperplastic polyps — common and usually low-risk
- Adenomas — and what tubular, villous, and dysplasia mean
- Sessile serrated lesions — flat, pale, easy to miss
- Less common types you might see named
- Why the same word can sit in different places on different reports
Hyperplastic polyps
A hyperplastic polyp is a small overgrowth of normal-looking cells. Under the microscope, the glands of the bowel lining are arranged in a regular saw-tooth pattern, but the cells themselves are not abnormal — there is no dysplasia (the disordered appearance that points toward later cancer risk). Hyperplastic polyps are most often found in the rectum and the sigmoid colon, and they tend to be small, pale, and easy to remove.
The current view is that small hyperplastic polyps in the lower colon do not, on their own, raise the risk of colorectal cancer in any meaningful way. They are removed because the endoscopist cannot tell from the surface whether a small flat polyp is hyperplastic or one of its serrated cousins. Once the pathologist has confirmed it as hyperplastic, the result is reassuring.
Hyperplastic polyps in the right colon, or unusually large hyperplastic polyps, are looked at more carefully because they may be reclassified as sessile serrated lesions on closer inspection.
Adenomas — and what the descriptors mean
An adenoma is a polyp made of glandular tissue with cells that are not normal but are not yet cancer. Adenomas are the polyp type most clearly linked to colorectal cancer through the slow stepwise process called the adenoma–carcinoma sequence. Most adenomas, given a typical lifetime, would never have become cancer; a minority would. Removing them interrupts the sequence.
Pathology reports describe adenomas in three ways that change the risk picture: their architecture, the degree of dysplasia, and the size.
Architecture: tubular, tubulovillous, villous
Adenomas are sorted by what the glands look like under the microscope. Tubular adenomas have round, regular gland openings and are the most common kind. Villous adenomas have long, finger-like projections; they are less common, tend to be larger, and carry a higher chance of containing more advanced features. Tubulovillous means a mixture of the two patterns. The shift from tubular to tubulovillous to villous represents a gradient of risk, not a sharp line.
Dysplasia: low-grade and high-grade
Dysplasia is the word pathologists use for cells that look out of order — nuclei that are too large, glands that are crowded or irregular, cells that have lost their normal organisation. Low-grade dysplasia is the usual finding in an adenoma and is part of why it is called an adenoma at all. High-grade dysplasia means the disorder is more pronounced, but the abnormal cells have not broken through the boundary that defines invasive cancer. High-grade dysplasia is not cancer; it is the step before, and it changes the follow-up plan.
Advanced adenoma
Several reports use the umbrella term advanced adenoma. The exact definition varies by guideline, but it generally means an adenoma that is at least 10 mm, or that has a villous component, or that contains high-grade dysplasia. The presence of one or more advanced adenomas tends to lead to a closer-than-average follow-up coloscopy.
Sessile serrated lesions
The sessile serrated lesion (SSL) — sometimes called a sessile serrated polyp or sessile serrated adenoma in older reports — was under-recognised for many years. These polyps are typically flat, pale, often covered with a thin film of mucus, and most often found in the right colon, where they hide against folds of bowel and can be easy to miss. Under the microscope, the glands have the same saw-tooth appearance as a hyperplastic polyp, but they are distorted at the base in a way the pathologist can identify.
Sessile serrated lesions matter because they are now thought to account for a meaningful share of colorectal cancers, particularly cancers that are diagnosed in the right colon between coloscopies. The pathway from sessile serrated lesion to cancer is different from the adenoma–carcinoma sequence at the molecular level — it is sometimes called the serrated pathway. Practically, an SSL is treated more like an adenoma than a hyperplastic polyp, and its presence can shorten the next coloscopy interval.
If your report mentions cytological dysplasia in a sessile serrated lesion, this is the equivalent of saying the cells inside are starting to look more disorganised — a development that warrants closer attention.
Less common but namable types
Traditional serrated adenoma is a rarer serrated polyp that is treated with similar caution to the sessile serrated lesion. Inflammatory polyps (sometimes called pseudopolyps) are heaped-up scar tissue seen in inflammatory bowel disease; they do not carry the same cancer risk as adenomas. Hamartomatous polyps — including juvenile polyps and Peutz–Jeghers polyps — are uncommon, and when multiple are seen they may prompt a conversation about an inherited syndrome. Lipomas, occasionally seen on coloscopy, are benign collections of fat in the bowel wall and not really polyps in the cancer-pathway sense at all.
Why the same word can mean different things on different reports
Pathology terminology has shifted over the last two decades. The same lesion that one laboratory now calls a sessile serrated lesion might have been called a sessile serrated adenoma, a sessile serrated polyp, or even a hyperplastic polyp on an older report. The term advanced adenoma has slightly different definitions in different guidelines. None of this is laxity; it reflects a field that has refined its categories as it has learned more.
Two practical implications: do not be alarmed if your most recent report uses unfamiliar wording; and if you are comparing today's findings with a much older report, expect some translation between vocabularies. The clinician reviewing the result should be able to map one onto the other.
What to ask your clinician
- What type of polyp was found — hyperplastic, adenoma, or sessile serrated lesion?
- If it was an adenoma, was the architecture tubular, tubulovillous, or villous?
- Was the dysplasia low-grade or high-grade?
- Were any features described as advanced — size at least 10 mm, villous component, or high-grade dysplasia?
- Were any sessile serrated lesions identified, and where?
- Given the type and number, when should I have the next coloscopy?
- Is anything about my findings worth mentioning to first-degree relatives?
Common worries, briefly addressed
The report says "adenoma" — does that mean cancer?
No. An adenoma is a polyp with low-grade abnormal-looking cells. It is the type that, over years, can become cancer if left, which is why it has been removed. The report would say the words carcinoma or invasive if cancer had been found.
Is a villous adenoma dangerous?
Villous architecture is a flag for closer follow-up because villous adenomas are more often larger and more often contain higher grades of dysplasia. The polyp itself is still a polyp, not a cancer. The reason for shorter intervals is precaution, not crisis.
The word "high-grade dysplasia" is frightening. What does it mean?
It means the cells look more disordered than usual, but they have not broken through the boundary that would make them invasive cancer. The standard response is complete removal, careful examination of the resection site, and a closer-than-average next coloscopy. It is not a cancer diagnosis.
Why do sessile serrated lesions get so much attention now?
Because the field learned, over the past two decades, that some colorectal cancers come from this pathway and that flat pale lesions in the right colon were being missed. Better detection — careful inspection, good preparation, sometimes a second look — is part of why coloscopy is more useful now than it was when these polyps were lumped in with hyperplastic polyps.
I had hyperplastic polyps only. Is that a "good" result?
Generally yes, especially if they were small and in the lower colon. Your follow-up will reflect that.
Sources
- U.S. Multi-Society Task Force on Colorectal Cancer — recommendations for follow-up after coloscopy and polypectomy
- European Society of Gastrointestinal Endoscopy — post-polypectomy coloscopy surveillance guideline
- World Health Organization classification of digestive system tumours — sections on colorectal polyps
- American Gastroenterological Association — clinical practice update on serrated polyposis syndrome and serrated lesions
- British Society of Gastroenterology — post-polypectomy and post-colorectal cancer resection surveillance guidelines
- American College of Gastroenterology — clinical guidelines on colorectal cancer screening