2781 Plexiform Angiomyxoid Myofibroblastic Tumor of the Gastric Cardia: An Uncommon Tumor With an Even Less Common Location

Abstract

INTRODUCTION: Plexiform angiomyxoid myofibroblastic tumor (PAMT) is a rare gastric tumor of stromal origin with unique immunohistochemical characteristics that differentiate it from other more common gastric stromal tumors. Since its first description in 2007, nearly all have been localized to the gastric antrum. We present a case of a symptomatic PAMT in the gastric cardia successfully treated with resection. CASE DESCRIPTION/METHODS: A 51 year old female complained of left sided abdominal pain, nausea, and early satiety. Esophagogastroduodenoscopy showed a 3 cm endophytic sub-epithelial mass in the posterior wall of the gastric cardia. Follow-up endoscopic ultrasound revealed an 18 mm × 33 mm hypoechoic mass contiguous with the muscularis propria (MP). Biopsies revealed a myxoid lesion composed of bland spindle cells, consistent with a PAMT. The patient was considered for resection given the proximity to the GEJ. Unfortunately, endoscopic management was unsuccessful and the patient subsequently underwent laparoscopic gastric wedge resection sparing the GEJ. Histologic exam revealed bland spindled cells within an eosinophilic fibromyxoid stroma with eosinophilic cytoplasm. While SMA and desmin stains were positive, C-Kit (CD117), DOG-1, and S-100 stains returned negative, confirming a PAMT. The patient’s postoperative course was uneventful at the six week follow-up with resolution of abdominal pain, nausea, and early satiety. DISCUSSION: PAMT is a rare benign tumor most commonly located in the antrum. Although patients are often asymptomatic, ulceration with bleeding, and obstruction are reported. It presents as a submucosal mass ranging from 2 cm – 15 cm. Diagnosis is histological with a nodular to plexiform growth pattern with well-circumscribed islands of spindle cells located within the MP and possible extension into the submucosa with ulceration. The tumor is composed of bland spindled cells separated by loose stroma with myxoid to fibromyxoid material. Cells are indistinct with eosinophilic cytoplasm, bland nuclei with inconspicuous nucleoli. Limited is known about progression of a PAMT but they appear to be slow growing with a good prognosis. Treatment largely consists of surgical resection, although endoscopic mucosal resection has been reported. This case presents a rare location of this rare tumor highlighting the importance of considering it with proximal gastric lesions.