EP.WE.412An unusual case of a 13.8cm Gastric Schwannoma invading into Transverse Mesocolon: A case report and literature review

Gastric Schwannomas (GS) are benign, slow-growing, Sub-mucosal tumours (SMT’s) that constitute 0.2% of all gastric tumours. They usually have a homogenous appearance on contrast enhanced computed tomography of the abdomen (CECT Abdomen) and rarely show malignant features such as irregular borders, calcification, local invasion and mucosal ulceration. Due to lack of mucosal changes and poor yield during Oesophago-Gastro-Duodenoscopy (OGD) and biopsy, they are often misdiagnosed as Gastro-Intestinal Stromal tumours (GISTs), a malignant SMT. Treatment options range from conservative management to major open resections and are dependent on the size and clinical presentation. Histologically, GS are spindle cells tumours with lymphoid cuffing. On Immunohistochemistry, they test positive for S100 but negative for DOG1, Smooth muscle actin and Desmin which are markers of GISTs. Here we present the case of a 61-year-old female with a 15-year history of epigastric fullness that turned out to be a 13.8cm GS originating from the greater curvature of the stomach. On CECT Abdomen, the tumour appeared heterogeneous, with multiple calcium deposits and local invasion into the transverse mesocolon. The patient underwent a Sub-total gastrectomy with en-bloc transverse colectomy. Symptoms from GS can be vague and can pose a significant diagnostic and investigative dilemma. Physicians and Surgeons should have a low threshold to investigate prolonged symptoms with CECT Abdomen. Despite their benign nature, if left undiagnosed, GS can grow to significant sizes and mimic malignant gastric tumours on conventional imaging resulting in unconventionally major resections.