Coeliac disease and malignancy of the duodenum: diagnosis by endoscopy, successful treatment of the malignancy, and response to a gluten free diet. A patient presented with subtotal villous atrophy and a malignant duodenal tumour of uncertain histogenesis. He was successfully treated by resection and chemotherapy and the small bowel mucosa recovered on a gluten free diet. The tumour was diagnosed at upper gastrointestinal endoscopy when barium studies and abdominal computed tomography were normal, thus making this one of the earliest coeliac malignancies diagnosed. 