Primary gastrointestinal non-Hodgkin lymphomas (NHL) account for about 0.9% of all gastrointestinal tract tumours. They are usually associated with ulcerative colitis, Crohn's disease, previous radiotherapy, renal transplantation and AIDS. We present a 36-year-old immunocompetent man, previously well with abdominal pain, weight loss and palpable mass in the right iliac fossa. A CT scan of the abdomen showed a thickening of the terminal ileum and the caecum with characteristic aneurysmal luminal dilation. Given the patient's presentation and radiology findings, a right hemicolectomy was performed. The suspected diagnosis of NHL, which was based on the imaging findings, was confirmed at histological analysis.