Intra-abdominal caecal desmoid tumour masquerading as gastrointestinal stromal tumour: a clinical insight.

Intra-abdominal desmoid tumours are rare, benign yet locally aggressive fibroblastic neoplasms that often mimic malignancies such as gastrointestinal stromal tumours (GIST) on imaging, making preoperative diagnosis challenging. We present the case of a woman in her mid-30s with a 6-month history of recurrent colicky abdominal pain and intermittent non-bilious vomiting during abdominal pain. Examination revealed a firm, mobile, non-tender mass in the right iliac fossa. Colonoscopy showed a submucosal caecal lesion without ulceration, and contrast-enhanced CT revealed a well-defined, heterogenous, enhancing lesion arising from the caecum suggestive of caecal GIST. Intraoperatively, a firm caecal mass with mesenteric fibrosis and terminal ileal dilatation was found. A limited right hemicolectomy was performed after a frozen section showed a spindle cell tumour. Immunohistochemistry demonstrated nuclear β-catenin positivity with negative C-kit (CD117), discovered on GIST 1 (DOG1), and desmin, confirming mesenteric desmoid fibromatosis. Surgery remains the mainstay of treatment in symptomatic cases.