A polyp is an abnormal tissue growth protruding from a mucous membrane, such as the lining of the colon or rectum. These common growths are typically discovered during a routine colonoscopy. Hyperplastic polyps are the most frequent type found in the large intestine, often located in the lower, or distal, portion of the colon and the rectum.
What Defines a Hyperplastic Polyp
The term “hyperplastic” refers to an overgrowth of normal, non-cancerous epithelial cells that form the lining of the intestine. This process involves an increase in the number of these cells, but they retain their normal appearance and organization. This differs from the cellular changes seen in adenomas, which involve dysplasia, or abnormal cell development considered precancerous.
Hyperplastic polyps are typically small, usually measuring less than five millimeters in diameter. They generally have a sessile shape, meaning they are flat or slightly dome-shaped without a defined stalk. When examined microscopically, the crypts display a characteristic serrated or sawtooth pattern caused by the folding of the epithelial cells.
These polyps are often pale and appear as smooth, nodular protrusions. While they can occur anywhere in the colon, their high frequency in the distal colon and rectum makes them common findings in screening examinations. The underlying cause of this cellular overgrowth appears to result from a failure of the mature surface cells to shed properly, leading to their accumulation.
Significance and Cancer Risk
The most important clinical characteristic of classic hyperplastic polyps is that they are classified as non-neoplastic, meaning they do not have the potential to develop into cancer. For the vast majority of patients, finding a hyperplastic polyp is a favorable outcome compared to the discovery of other polyp types. These lesions carry a very low risk of malignant transformation.
The significance of these polyps lies in the need for an accurate diagnosis, as they belong to a broader category of growths called serrated polyps. This serrated group also includes sessile serrated lesions (SSLs), which carry malignant potential and are considered a precursor to colorectal cancers. Because the two types can look similar during an endoscopy, polyps are removed and analyzed by a pathologist to distinguish them definitively.
Classic hyperplastic polyps tend to be smaller and are most often found in the rectum and sigmoid colon, the lower parts of the large intestine. In contrast, the more concerning SSLs are typically larger, often found in the upper, or proximal, colon, and exhibit specific cellular features under the microscope that denote their higher risk. Pathologists confirm the diagnosis by looking for the absence of cellular atypia and the distinct growth pattern of the epithelial cells.
Follow-Up and Surveillance
The diagnosis of a small, classic hyperplastic polyp has a favorable impact on a patient’s recommended surveillance schedule. If a patient’s colonoscopy reveals only small hyperplastic polyps, typically less than 10 millimeters and located in the distal colon or rectum, the finding is generally considered equivalent to a normal colonoscopy. The American College of Gastroenterology and other governing bodies reflect this low-risk status in their guidelines.
These patients are usually returned to the standard, average-risk screening interval, meaning their next colonoscopy would be recommended in 10 years. This is a key difference from patients found to have adenomas or SSLs, which necessitate accelerated surveillance with follow-up colonoscopies recommended much sooner, often within three to five years. The decision to return a patient to a 10-year interval underscores the medical community’s confidence that these specific polyps pose no significant threat.
However, if a patient is found to have an unusually large number of hyperplastic polyps, or if they are large and located in the proximal colon, doctors may recommend a shorter follow-up time. In these specific cases, the polyps may be reclassified or treated with greater caution due to the possibility of a less common condition called serrated polyposis syndrome, which carries an increased cancer risk.