Abstract

Extragastrointestinal stromal tumour (EGIST) occurs outside the gastrointestinal tract and has histopathological and molecular characteristics similar to gastrointestinal stromal tumour (GIST). This tumour is rare and aggressive. A male patient was admitted with anaemia and lower limb oedema. CT scan showed a tumour in the mesentery and retroperitoneum, suspected to be a small bowel GIST. During laparotomy an unresectable mass was found compressing the retroperitoneal structures. Pathology and immunohistochemistry (CD117) confirmed an EGIST. EGIST arises from Cajal-like cells or from pluripotent stem cells outside the gastrointestinal tract. It is aggressive and has a worse prognosis than GIST. Immunohistochemistry is crucial for diagnosis. Surgery aimed at debulking as much of a tumour mass as possible is the cornerstone of treatment. The role of imatinib is not clear. EGIST is rare and has a bad prognosis, and there is no consensus on grading and management. A low threshold of suspicion is crucial for early diagnosis.