1925 GIST Kidding: Primary Gastric Synovial Sarcoma Presenting as Hematemesis

Abstract

INTRODUCTION: Synovial sarcoma (SS) is an uncommon subtype of mesenchymal derived solid tumors that is characterized by its unique histologic pattern. It is most often found in the extremities and rarely, the digestive tract, which can lead to gastrointestinal bleeding. Gastric tumors of mesenchymal origin often have overlapping radiographic and endoscopic appearances, which presents a significant challenge in diagnosis. We report one of only 3 confirmed cases of primary gastric synovial sarcoma of the lesser curvature in a patient who presented with hematemesis. CASE DESCRIPTION/METHODS: A 26-year-old male presented with a two-week history of worsening abdominal pain and intermittent hematemesis. He denied any history of hematochezia, melena, early satiety, weight loss, recent NSAID use or alcohol ingestion. Exam was notable for epigastric tenderness without rebound or guarding. Labs revealed microcytic anemia and thrombocytopenia without transaminitis or elevated lipase. Abdominal CT showed an 8 cm mass along the posterior gastric body with suspicion for intratumoral hemorrhage, highly suggestive of a gastrointestinal stromal tumor (GIST) [Figure 1]. EGD revealed a large, ulcerated, non-bleeding, non-circumferential, submucosal mass on the lesser curvature of the stomach, also concerning for a GIST [Figure 2]. Endoscopic ultrasound showed neither hepatic invasion nor lymphadenopathy. Partial gastrectomy pathology supported the endoscopic biopsy results, which showed high grade, monophasic, atypical spindle cells with t(X;18)(SYT-SSX) chromosomal translocation by fluorescence in situ hybridization (FISH). Immunohistochemistry (IHC) was strongly positive for TLE1 staining, but negative for C-KIT and DOG-1, to which GISTs are immunoreactive, confirming a diagnosis of primary gastric synovial sarcoma [Figure 3]. He tolerated 6 cycles of sarcoma-directed chemotherapy without evidence of progressive disease. DISCUSSION: Intramural gastric spindle cell malignancies are difficult to distinguish from one another, and require different disease-tailored therapies. Though GISTs account for 90% of these tumors, other rare pathologies exist. These include synovial sarcomas, which are characterized by a variable degree of epithelial differentiation associated with a disease-specific gene translocation. In patients with hematemesis found to have endoscopic and radiographic findings suspicious for GIST, ICH and FISH analyses are crucial to differentiate between mesenchymal malignancies to guide effective therapy.