Invasive inflammatory fibroid polyp of the stomach: a case report and literature review

Abstract

Background: Inflammatory fibroid polyps (IFPs) are rare mesenchymal lesions that affect the gastrointestinal tract. IFPs are generally considered benign, noninvasive lesions; however, we report a case of an invasive gastric IFP. To the best of our knowledge, this is only the second case report of an invasive gastric IFP.

Case presentation: A 62-year-old woman presented with complaints of epigastric pain and vomiting. Computed tomography showed a 27-mm, hyper-enhancing tumor in the prepyloric antrum. Upper endoscopy also showed a submucosal tumor causing subtotal obstruction of the gastric outlet. Because a gastrointestinal stromal tumor was suspected, distal gastrectomy was performed. Histopathological examination revealed spindle cell proliferation in the submucosal layer. The spindle cells had invaded the muscularis propria layer and extended to the subserosal layer. The tumor was finally diagnosed as an IFP based on immunohistochemical findings. No mutations were identified in the platelet-derived growth factor receptor alpha (PDGFRA) gene via molecular genetic analysis.

Discussion and conclusions: After the discovery that IFPs often harbor PDGFRA mutations, these growths have been considered neoplastic lesions rather than reactive lesions. Based on the present case, IFPs might be considered not only neoplastic but also potentially invasive lesions.

Keywords: Inflammatory fibroid polyp; Invasion; Platelet-derived growth factor receptor alpha mutation; Stomach.

Fig. 1

Computed tomography (CT) findings. a Axial view. b Coronal view. c Sagittal view. CT image showing a hyper-enhancing tumor in the submucosa of the prepyloric antrum (arrows). CT showing a thickening of the muscularis propria layer and a hyper-enhancing lesion in the subserosa of the gastric antrum (arrow heads)

Fig. 2

Endoscopic findings. a Upper endoscopy showing a submucosal tumor at the prepyloric antrum causing obstruction of the gastric outlet. b Endoscopic ultrasound showing a hypoechoic tumor located in the submucosal layer

Fig. 3

Macroscopic findings. The resected specimen revealed circumferential wall thickening of the prepyloric antrum (red line: cut line). Cut-section reveals thickening of the submucosal layer and the muscularis propria layer (red square: A cut surface of the resected specimen shown in Fig. 4a)

Fig. 4

Microscopic findings. a Histopathological view through a low-power microscope. b-e Histopathological view through a medium-power microscope. Microscopic findings reveal spindle cell proliferation and infiltration of lymphocytes and plasma cells in the submucosal layer. Cells invading the muscularis propria layer (arrows) and extending to the subserosal layer (arrowheads)

Fig. 5

Immunohistochemical findings. Immunohistochemical findings revealing spindle cells stained positive for CD34 and smooth muscle actin but negative for CD117, DOG-1 and S100 protein. The Ki-67 labeling index was less than 1%. Scattered mast cells stained positive for CD117, but the spindle cells stained negative. Adipose tissue engulfed by the lesion stained positive for S100 protein, but the spindle cells stained negative