Gastric Plexiform Fibromyxoma: A Rare Clinical Entity

Abstract

Abstract Introduction/Objective Plexiform fibromyoma (PF) tumors are benign mesenchymal tumor that arises in the antrum and pyloric region of the stomach. PF are recently added to the WHO classification of tumors in 2010. To the best of our knowledge; there are less than 100 cases have been reported. Methods/Case Report We present a case of 41-year-old Caucasian female who presented for EGD in preparation for her bariatric surgery in which she was found to have an incidental large subepithelial mass lesion with small surface ulceration in the proximal stomach. Fine needle biopsy was performed showing bland spindle cell proliferation with myxoid background. Computed tomography (CT) revealed an enhancing, highly vascular exophytic submucosal mass in the anterior wall of the gastric antrum, indicating a GIST. Resection of the mass showed a 6.5 cm bulging mass covered by mucosa with tan white focally cystic cut surfaces. Histologically, the tumor is composed multinodular plexiform growth pattern the presence of spindle cells in the myxoid or fibromyxoid stroma rich in arborizing thin- walled vessels. The spindle tumor cells contained round or ovoid nuclei and scanty eosinophilic cytoplasm. Some cells exhibited perinuclear cytoplasmic haloes. Lymphocytes and mast cells were observed in the stroma. There was no significant cytological atypia or necrosis in the tumor cells, and mitotic activity was negligible. Immunohistochemical stains showed the spindle cells to be strongly positive for SMA, desmin and vimentin while negative for CK AE1/AE3, CK CAM 5.2, DOG1, S100, CD45, CD117. Meanwhile Ki-67 shows a proliferation index of less than 2%. The overall morphological and immunohistochemical findings are supportive of the above diagnosis of plexiform fibromyxoma. The main differential diagnosis is GIST, which is the main gastric mesenchymal tumor, also a lot of PF were misdiagnosed as GIST. Genetic testing was described in some PF that showed metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and glioma-associated oncogene homolog 1 (GLI1) gene translocation. Results (if a Case Study enter NA) NA. Conclusion Plexiform fibromyoma tumors seem to follow a benign course after complete excision by distal gastrectomy. To date no lymph node or distant metastasis is reported.