AB177. An unusual cause of right iliac fossa pain in a middle-aged gentleman

Background: Gastrointestinal stromal tumours (GISTs) are characterised in adults by expression of CD117 antigen, and account for <1% of gastrointestinal tumours, with a mean age at diagnosis of 64. GISTs are thought to derive from the Interstitial Cells of Cajal, and cellular morphology varies from spindle-like (70%) to epithelioid (20%) to mixed (10%). The clinical presentation is varied and includes: abdominal pain (8% to 17%), gastrointestinal bleeding (28%), an acute abdomen (2% to 14%), asymptomatic abdominal mass (5%) and increasingly incidental findings on imaging performed for another reason (13% to 18%).

Methods: We present the case of a 59-year-old gentleman who was admitted via the emergency department with a 2/7 history of dull right iliac fossa (RIF) pain on a background 2/52 history of intermittent loose stool. He had no past medical or surgical history. On examination there was localised rebound tenderness in the RIF. Blood results included: CRP 12, WBC 9.4 and Hb 15.1. Computed tomography showed a ‘2.5 cm rounded well defined heterogeneous structure with significant surrounding inflammation inseparable from the distal ileum’. The patient underwent an elective laparoscopic, converted to open, small bowel resection two weeks later.

Results: Histology identified a polypoid mass, 2 cm in diameter, microscopically identified as a GIST.

Conclusions: The clinical behaviour of GISTs is highly variable with the main prognostic determinants being tumour size, mitotic rate, and tumour location. The imaging modality of choice is CT with contrast, and this case highlights the need for radiological input in this age group when investigating RIF pain.

Keywords: Gastrointestinal stromal tumour (GIST); Interstitial Cells of Cajal; CD117 antigen