An 83-year-old woman with a history of non-insulin-dependent diabetes mellitus, arterial hypertension, dyslipidaemia and chronic atrial fibrillation consulted for progressive abdominal pain and constitutional syndrome of one month's duration. On physical examination, the patient was afebrile and haemodynamically stable, with a globular, soft, depressible abdomen, painful on palpation and a tumour on the left flank. Blood tests showed haemoglobin 9.3 g/dl, leukocytes 11,300 /mm3, urea 109 mg/dl, creatinine 1 mg/dl, total bilirubin 2.6, alkaline phosphatase 139 U/l, with the rest of the liver function normal. Abdominal computed tomography (CT) scan showed a mass measuring 20 x 20 x 15 centimetres of heterogeneous density that caused displacement of the renal vessels and pyelocaliceal system without causing obstructive uropathy or metastatic involvement. Surgery involved a radical left nephrectomy with complete excision of the mass. The patient died one month after surgery due to acute pulmonary oedema. Pathological anatomy showed a 3.5 kg tumour of mucoid appearance with areas of haemorrhage affecting 30%, and in its centre the rejected nephrectomy specimen but without parenchymal infiltration, compatible with a mixed liposarcoma (dedifferentiated and myxoid), with a mitotic index of 2/10 high magnification fields.