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Inflammatory polyp of the stomach

What is an inflammatory polyp in the stomach?

An inflammatory polyp is a non-cancerous growth that develops from the tissue that lines the inside of the stomach. It is called a polyp because it often sticks out from the surface of the tissue. Inflammatory polyps are also called hyperplastic polyps.

The stomach

The stomach is part of the gastrointestinal tract. When we eat, food enters the mouth and travels down the esophagus into the stomach. Once in the stomach, the food is mixed with a strong acid which breaks the food down into very small particles. This process is called digestion. The digested food particles are then either absorbed into the bloodstream or removed from the body as waste.

The tissue on the inner surface of the stomach is made up of specialized epithelial cells that form a barrier called the epithelium. The cells at the top of the epithelium are called foveolar cells and they protect the stomach from the strong acid used to break down food. Underneath the surface epithelium is a thin layer of tissue called the lamina propria which supports the surface cells. Together, the surface epithelium and lamina propria are called the mucosa.

What causes an inflammatory polyp?

Inflammation within the lining of the stomach is called gastritis. Inflammation that is new or that is causing ongoing damage is called active inflammation. Inflammation that has been present for a long period of time is called chronic inflammation. Depending on the cause, both active and chronic inflammation can be seen in the stomach at the same time.

Most inflammatory polyps in the stomach are caused by long-standing inflammation. Chronic gastritis is a term pathologists use to describe long-standing inflammation in the stomach and anything that causes chronic gastritis in the stomach can lead to the development of an inflammatory polyp. The most common causes of chronic gastritis are infection of the stomach with Helicobacter pylori, bile reflux, and autoimmune gastritis.

How do pathologists make this diagnosis?

The diagnosis of inflammatory polyp is usually made after part or all of the polyp is removed during a procedure called endoscopy. This procedure involves using a camera attached to a long tube to see the inside of the stomach. The tissue removed is then sent to a pathologist for examination under the microscope.

When examined under the microscope, inflammatory polyps show an increased number of foveolar cells which makes epithelium look disorganized. Large open or dilated spaces may also develop. The connective tissue or stroma surrounding the foveolar cells usually shows signs of inflammation including an increased number of inflammatory cells such as plasma cells, lymphocytes, and neutrophils.

Because inflammatory polyps can be caused by infection of the stomach with a bacteria called Helicobacter pylori, your pathologist may perform tests such as special stains or immunohistochemistry to look for the bacteria in the tissue sample. Both of these tests make it easier to see the bacteria which are very small and difficult to see on a hematoxylin and eosin-stained (H&E) slide.

Intestinal metaplasia

Long-standing inflammation or chronic 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 and pathologists describe the specific type of metaplasia that takes place in the stomach as intestinal metaplasia. Intestinal metaplasia may be found in some inflammatory polyps. If your pathologist sees intestinal metaplasia in the tissue sample, it will be described in your report.

Dysplasia

Dysplasia is a word pathologists use to describe an abnormal pattern of growth. Like intestinal metaplasia, dysplasia can develop in patients who have had long-standing inflammation or chronic gastritis for many years.

Dysplasia is not typically seen in an inflammatory polyp but when seen it will be described in your report. Pathologists divide dysplasia into low and high grades based on how abnormal the tissue looks when examined under the microscope.

Dysplasia is a non-cancerous change. However, it is considered a precancerous condition because it increases the risk of developing a type of stomach cancer called adenocarcinoma over time. The risk of cancer is higher with high-grade dysplasia.

Syndromes associated with hyperplastic polyps

For most patients, inflammatory polyps are unrelated to any preexisting genetic condition. Some patients, however, inherit genetic changes that put them at a higher risk of developing multiple inflammatory polyps as well as other non-cancerous growths.

These patients are said to have a syndrome and the most common syndromes associated with inflammatory polyps are Peutz-Jeghers, Cowden, and Juvenile polyposis.

In these syndromes, specific genes that normally prevent our cells from growing and dividing too rapidly or in an uncontrolled way, are altered or mutated. This causes uncontrolled cell growth and the development of a non-cancerous polyp.

by Jason Wasserman, MD FRCPC (updated September 18, 2021)
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