Extraskeletal Ewing sarcoma of the duodenum presenting as duodenojejunal intussusception

Investigations showed a haemoglobin concentration of 8·1 g/dL, platelet count of 565 × 109 per L (normal 150–400), and white cell count of 10·5 × 109 per L; the mean corpuscular volume was 77·2 fL (normal 80–94) and the mean corpuscular haemoglobin was 23·1 pg per cell—suggestive of iron deficiency anaemia. Immunohistochemistry stains demonstrated strong and diffuse nuclear immunoreactivity to NKX2-2 and ERG, with membranous immunoreactivity to CD99, and an absence of nuclear immunoreactivity to FLI1: supporting a possible fusion of the EWSRI gene on chromosome 22q12 with the gene encoding the transcription factor ERG (appendix). Young adults presenting with recurrent vomiting, weight loss, an abdominal mass, and anaemia should raise the suspicion of an aggressive malignancy (video).