S6426 The Swan Inside: Not All Tumours Are Ugly Ducklings

Introduction: Gastric schwannoma is a rare mesenchymal tumor, making up about 0.2% of all gastric tumors and 4% of benign gastric neoplasms. The stomach is the most common site of occurrence within the gastrointestinal tract. These tumours typically affect older adults, with a noted female predominance, median age around 60 years, and malignant transformation is very rare. Here, we present a case of symptomatic gastric schwannoma diagnosed by endoscopic biopsy and managed with robotic wedge resection. Case Description/Methods: Our patient was a 54-year-old woman when she presented to the Emergency Department with complaints of sharp abdominal pain, left more than the right, associated with nausea and vomiting. Computed tomography (CT) Scan done at the time revealed epiploic appendagitis, suspicious for neoplasm. She was scheduled for esophagogastroduodenoscopy, which revealed a 2.3-3 cm semi-pedunculated polypoid gastric mass with an umbilicated centre. The overlying mucosa was smooth, featureless, with no ulcers or friability. The umbilicated portion was superficially ulcerated. Gastric mucosa was otherwise normal throughout. Biopsy samples revealed schwannoma, hence she underwent robotic endoscopic wedge resection for removal of the tumor. Discussion: Gastric schwannomas, also known as neurinomas, are benign neurogenic tumours originating from Schwann cells, which are responsible for myelination of peripheral nerves. While these tumours most commonly arise in the head and neck region, they may rarely occur within the gastrointestinal (GI) tract, with the stomach being the most frequently involved site, followed by the colon. Gastric schwannomas are typically slow-growing, and most people remain asymptomatic. However, in certain cases they may present with non specific symptoms such as abdominal pain, as seen in our patient, gastrointestinal bleeding, or an abdominal mass. Diagnosis is often confirmed through immunohistochemical staining, which characteristically demonstrates strong positivity for S-100 protein, distinguishing it form other mesenchymal tumours such as gastrointestinal stromal tumours (GISTs). In our case, endoscopic biopsy confirmed the diagnosis of schwannoma, prompting robotic endoscopic wedge resection. Complete surgical excision is the treatment of choice, with excellent prognosis and no reported cases of recurrence or metastasis in long-term follow up. Accordingly, routine surveillance with endoscopic post resection is not typically indicated.