An inflammatory fibroid polyp is a rare, noncancerous growth that most often develops in the stomach. Despite its name, it is not caused by inflammation. It is a benign tumor that starts in the submucosa, the tissue layer just below the inner lining of the stomach or bowel. Doctors sometimes call it a Vanek tumor, after the doctor who first described it in 1949.
An inflammatory fibroid polyp does not spread to other parts of the body, and it has never been reported to turn into cancer. Removing the polyp completely is usually the only treatment needed. This article explains what an inflammatory fibroid polyp is, how pathologists recognize it, and what the findings in your pathology report mean.
Inflammatory fibroid polyps are uncommon and make up only 0.1% to 3% of all polyps found in the stomach. They are most often found in adults in their 60s and 70s. Both men and women can develop them, and they are very rare in children.
About 70% of inflammatory fibroid polyps develop in the stomach, usually in the lower part called the antrum, near the opening to the small intestine. About 20% develop in the small intestine. A small number are found in the colon or the esophagus.
For many years, doctors believed an inflammatory fibroid polyp was a reaction to injury or inflammation. Research has since shown that most of these polyps are true tumors driven by a change in a single gene called PDGFRA. Between 55% and 74% of inflammatory fibroid polyps carry a mutation in this gene. The mutation switches on a growth signal inside the polyp cells, which causes them to multiply and form a mass.
In almost all people, the PDGFRA mutation is found only in the polyp cells and is not inherited. Very rarely, the mutation is present in every cell of the body and can be passed down in families. People with this inherited condition can develop several inflammatory fibroid polyps, sometimes along with other growths in the digestive tract. Your doctor may suggest genetic counseling if you have several polyps or a family history of similar growths.
An inflammatory fibroid polyp is different from a hyperplastic polyp, which is sometimes called an inflammatory polyp. A hyperplastic polyp forms in the inner lining of the stomach as a response to long-lasting inflammation. An inflammatory fibroid polyp starts in the deeper submucosa and is caused by a genetic change in the polyp cells.
Many inflammatory fibroid polyps cause no symptoms and are found incidentally during an upper endoscopy for another reason. When symptoms do occur, they depend on the polyp’s size and location.
The diagnosis of an inflammatory fibroid polyp is made after a pathologist examines tissue from the polyp under a microscope. The tissue may come from a biopsy, from a polypectomy performed during endoscopy, or from a surgical procedure to remove part of the stomach or bowel.
Under the microscope, an inflammatory fibroid polyp is made up of long, thin spindle cells that look bland and regular. These cells sit in a loose, pale background tissue that contains many small blood vessels. The spindle cells often wrap around the blood vessels in rings, a pattern pathologists describe as onion-skinning.
Mixed in with the spindle cells are many immune cells, especially eosinophils. These immune cells explain the word “inflammatory” in the name, even though inflammation does not cause the polyp. The polyp surface may show an erosion or ulcer, where the lining has broken down.
Immunohistochemistry is a test that uses antibodies to show which proteins are present in cells. Pathologists use this test to confirm the diagnosis of an inflammatory fibroid polyp and to rule out other spindle cell tumors that can look similar. The most important of these is a gastrointestinal stromal tumor (GIST), which can spread to other parts of the body and needs different treatment. Your report may describe the following results.
A margin is the edge of the tissue that was cut to remove the inflammatory fibroid polyp. Pathologists examine the margins to see whether the polyp was removed completely. Because this polyp starts in the submucosa, it may reach the deep margin, which is the cut edge at the bottom of the tissue.
A negative margin means no polyp cells are seen at the cut edge, and the polyp was likely removed completely. A positive margin means polyp cells are seen at the cut edge, and some of the polyp may have been left behind. A positive margin does not mean the polyp is cancer, but it slightly increases the chance that the polyp will grow back.
The outlook for a person with an inflammatory fibroid polyp is excellent. The polyp does not spread to other parts of the body, and no cases of inflammatory fibroid polyps turning into cancer have been reported. Most people are cured once the polyp is removed completely. The polyp rarely grows back, and most of those cases occurred because the polyp was not completely removed during endoscopy.
After an inflammatory fibroid polyp is diagnosed, the main goal is to ensure the entire polyp has been removed. If the polyp was removed completely, most people need no further treatment. Your doctor may suggest a follow-up endoscopy to check the area if the margin was positive or the polyp was removed in pieces.
If the diagnosis was made on a small biopsy, your doctor will usually recommend removing the rest of the polyp. Smaller polyps can often be removed during endoscopy. Larger polyps, or polyps that block the stomach or bowel, may need surgery. Because these polyps are benign, chemotherapy and radiation are not used.