Retroperitoneal liposarcoma is a rare solid tumour of mesenchymal origin with an incidence of 2.5
per million population. We report what is, to the best of our knowledge, the fi rst case in the English
literature of retroperitoneal liposarcoma in an adult patient with Down syndrome. The tumour was
surgically resected with no use of adjuvant chemotherapy or radiation. No recurrence was found at
follow-up 2 months postoperatively. Clinicians should consider retroperitoneal liposarcoma in the
differential diagnosis of abdominal distention in adult patients with Down syndrome.