Abstract
Extra gastrointestinal stromal tumour(EGIST) is rare and is regarded as gastrointestinal stromal tumour(GIST) that originates outside of the gastrointestinal tract. They originate from other intraabdominal tissues such as the omentum, mesentery and peritoneum. The cell of origin is the interstitial cell of Cajal(ICC), a pacemaker cell that controls gastrointestinal peristalsis and the tumor is characterized by the expression of KIT(CD117) a transmembrane tyrosine kinase receptor. Here, a 49-year-old female who presented with a 6 month history of abdominal pain, progressive abdominal swelling and the presence of an upper abdominal mass. She had surgical resection and adjuvant imatinib for the intraabdominal mass diagnosed on histology and immunohistochemistry as EGIST of the lesser omentum. Serial CT 14 months after surgery revealed no evidence of recurrence or metastasis. Clinicians should consider EGIST in the differential diagnosis of abdominal masses.