This article was last reviewed and updated on April 26, 2018.
by Shaheed Hakim, MD FRCPC
A hyperplastic polyp is a non-cancerous growth that develops in the stomach.
It is called a polyp because it often sticks out of the tissue that lines the inner surface of the stomach.
There are many causes for hyperplastic polyps although the most common is infection of the stomach by a bacteria called Helicobacter.
The normal stomach
The stomach is a hollow organ located in the middle of your abdomen. The stomach is responsible for breaking down and absorbing food so that it can be used by your body.
The inner surface of the stomach is lined by specialized cells called foveolar cells which form a barrier called an epithelium. This barrier protects the stomach from the acid that aids in the digestion of our food.
Inflammation in the stomach
Anything that causes irritation of the epithelium can lead to short term (acute/active inflammation) or long term inflammation (chronic inflammation) of the stomach, a process that pathologists call gastritis. The lining of the stomach will try to regenerate and repair the damage caused by the inflammation, however, excessive regeneration can lead to an increased number of foveolar cells and a process referred to as hyperplasia.
What is a hyperplastic polyp?
Hyperplastic polyps are non-cancerous (benign) growths that develop from the epithelium in the stomach. Hyperplastic polyps are also called inflammatory polyps. Both polyps are thought to represent a spectrum of ongoing inflammation (inflammatory polyp) and regeneration/repair (hyperplastic polyp).
Common causes of gastritis and the development of hyperplastic polyps are infection, bile reflux, and autoimmune gastritis.
One of the most common causes of gastritis is infection of the stomach by a bacteria known as Helicobacter. Pathologists often use ‘special stains’ that can highlight the small Helicobacter organisms making for more easy and accurate identification.
Long-term and ongoing inflammation (chronic active gastritis) that is not treated can damage the foveolar epithelium. If the damage continues for many years, a new type of epithelium similar to the epithelium normally found in the small intestine slowly replaces the foveolar epithelium.
The change from foveolar epithelium to small intestinal epithelium is an example of metaplasia. This specific type of metaplasia that takes place in the stomach is referred to as intestinal metaplasia.
Dysplasia refers to an abnormal pattern of growth that is initially non-cancerous (benign) but can turn into cancer. If left untreated, long term inflammation (chronic gastritis) and intestinal metaplasia, can then lead to dysplasia.
The earliest change is referred to as ‘low-grade’ dysplasia. In some cases, the cells become even more abnormal and progress to ‘high-grade’ dysplasia.
In high grade dysplasia, the abnormal cells look similar to cancer cells but are only seen in the epithelium. Once the cells have traveled into the tissue below the epithelium, the diagnosis changes to ‘intramucosal carcinoma’, which is essentially an early stage cancer. The movement of cancer cells out of the epithelium into the surrounding tissue is called invasion.
Most hyperplastic polyps do not contain dysplasia.
For most patients, hyperplastic polyps are sporadic, that is they are unrelated to any preexisting genetic condition. Some patients, however, inherit genetic changes that put them at a higher risk of developing multiple hyperplastic polyps as well as other non-cancerous (benign) growths.
In these syndromes, specific genes that normally prevent our cells from growing and dividing too rapidly or in an uncontrolled way, are mutated. This causes uncontrolled cell growth and the development of a non-cancerous polyp.