Inflammatory fibroid polyp - gastrointestinal tract

Last revised by Raymond Chieng on 7 Jun 2023

Inflammatory fibroid polyps (IFP's) are rare, benign lesions of the gastrointestinal tract, most commonly affecting the gastric antrum, followed by small bowel, and large bowel 1. Rarely it occurs in rectum, esophagus or gall bladder 1.

The tumor is most commonly found in in patients aged 60-70 years old 2.

In 66-75% of the cases, it occurs in the gastric antrum, followed by small bowel (18-20%), colon and rectum (4-7%). Rarely, it occurs in gall bladder, esophagus, and duodenum (incidence of 1% each). Very rarely, it occurs in the appendix (less than 1%) 1.

Inflammatory fibroid polyps usually do not cause symptoms 1. It is usually found incidentally during endoscopic procedures or laparotomy 1.

However, if they do cause symptoms, the presentation depends upon the location of the lesion 1. Abdominal pain is the main symptom when the lesion is found in the stomach. When the lesion is found in the small bowel, it can cause intussusception or intestinal obstruction 1. Other less common symptoms are: vomiting, loose stools, bloody stools, tenesmus, and altered bowel habits 1.

IFP sizes usually range from 2 to 5 cm in diameter. However, sizes up to 20 cm do occur 1. It arises from the submucosa, growing into the lumen 1. Like gastrointestinal stromal tumor (GIST), it arises from the development of mesenchymal cells of the intestinal tract, due to mutations in platelet derived growth factor receptor alpha (PDGFRA) 2.

It consists of mononuclear and spindle-shaped cells, forming a whirl-like structure around the blood vessels 2. Other inflammatory cells such as eosinophils, lymphocytes, macrophages, and mastocytes can also be present within the polyp 1.

Immunohistochemistry can differentiate IFP from other tumors such as GIST, plexiform fibromyxoma, and schwannoma. IFP stains positive for CD 34 and vimentin 1, while stains negatively for CD 117, S100, and DOG 1. GIST not only stains positive for CD 34 and vimentin, it is also positive for CD 117 and DOG 1. Plexiform fibromyxoma lacks concentric blood vessels and CD 34 negative. Schwannoma generally has lymphocyte cuffing around the blood vessels and S100 positive.

It manifests as well-defined, ovoid, lobulated, contoured endoluminal mass. Mucosal hyperenhancement may be present in those with mucosal involvement or ulcerations. The polyp itself can range from hypodense to hyperdense when compared to surrounding soft tissues 3. Intestinal IFPs generally are hypodense when compared to gastric IFPs 3.

IFP is a benign tumor. If the tumor is found incidentally during endoscopy, local excision is the gold standard treatment 2.

Inflammatory fibroid polyp was first described by Vanek as a benign mesenchymal lesion in 1949 in a case series of six patients 1. In 1953, the word "inflammatory fibroid polyp" was first coined by Helwig and Ranier 4.

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