# Reactive Nodular Fibrous Pseudotumor Presenting as Gastric Outlet Obstruction in a Young Adult Male Patient: A Case Report and Review of the Medical Literature

## TL;DR

A young adult male presented with a rare gastric tumor causing blockage, diagnosed as a reactive nodular fibrous pseudotumor.

## Contribution

This case highlights unique features of a rare pseudotumor, including calcifications and IgG4-positive plasma cells.

## Key findings

- The patient had a 5.6 cm fibrotic gastric mass with calcifications and lymphoplasmacytic inflammation.
- Immunohistochemistry showed IgG4-positive plasma cells and absence of CD117 expression.
- The case emphasizes the importance of histopathological evaluation for accurate diagnosis.

## Abstract

Mesenchymal proliferations involving the gastrointestinal tract are uncommon and often unexpected upon initial clinical presentation. Here, we are reporting a case of a 20‐year‐old male patient presenting to the hospital with abdominal pain and vomiting. Upon evaluation, the patient was initially discharged home on antacid therapy. The symptoms progressed in intensity, and a subsequent CT scan was remarkable for marked gastric expansion and a prepyloric mass. The macroscopic examination of the resected lesion revealed a 5.6 cm multilobular fibrotic mass involving the gastric wall. Microscopic analysis was notable for a spindle‐cell lesion with admixed lymphoplasmacytic inflammation, patchy necrosis, and calcifications. The immunohistochemical workup was suggestive of a reactive nodular fibrous pseudotumor. This case is notable for several aspects, including the acute clinical presentation, intralesional calcifications, abundant IgG4‐positive plasma cells, and lack of CD117 immunohistochemical expression. The peculiarities of the case and a review of the medical literature will be presented.