Background: Plexiform fibromyxoma, also known as a plexiform angiomyxoid myofibroblastic tumor, is a relatively new pathological entity described for the first time in 2007. This tumor is a very rare mesenchymal non-gastrointestinal stromal tumor (non-GIST) with fewer than 100 cases.
Case Summary:A 26-year-old woman presented with epigastric pain. Upper gastrointestinal endoscopy and endoscopic ultrasound revealed a gastric well-circumscribed, submucosal mass. A gastrointestinal stromal tumor (GIST) was suspected.
The patient underwent an atypical gastrectomy. The gross specimen showed a submucosal well limited glossy white tumor. Microscopic study showed a hypocellular proliferation composed of bland spindle cells set in a fibromyxoid matrix with a rich arborizing thin-walled capillary network. Spindle cells were organized in a fascicular pattern. Immunohistochemical studies revealed high reactivity for Smooth Muscle Actin (SMA), focal reactivity for Desmin with no staining for c-KIT, DOG1. The diagnosis of gastric plexiform fibromyxoma was then made.
The patient had a favorable prognosis without relapse or metastasis during the 2-year follow-up after the surgery.
Conclusion:Plexiform fibromyxoma is a very rare mesenchymal tumor with numerous similitudes to gastrointestinal stromal tumor (GIST). Immunohistochemistry is the basis of the differential diagnosis.
