Misdiagnosed as osteosarcoma: Brown tumour in a haemodialysis patient
A 26‐year‐old woman was referred to our hospital for a 10‐day history of dull pain in her left knee. She had been attending haemodialysis three times a week for 7 years. Serum intact parathyroid hormone (iPTH), alkaline phosphatase, calcium and phosphorus were 379.2 pg/mL, 452 U/L, 2.37 mmol/L and 1.06 mmol/L, respectively. 99mTc‐MDP bone SPECT showed hypermetabolic spots on the left distal femur and ankle (Suppl. Fig. S1). She suffered a left ankle injury on admission. Computed tomography (CT) three‐dimensional reconstruction and contrast enhanced MRI revealed it was an osteolytic lesion and soft‐tissue mass in the distal femur (Fig. 1a, b). The diagnosis of osteosarcoma was established and gross‐total resection was planned, but the preoperative histopathological examination verified it was a brown tumour (Fig. 1c). So curettage and bone grafting was carried out.
Brown tumour is usually regarded as a benign skeletal complication of primary and secondary hyperparathyroidism (HPT). Secondary HPT is a frequent complication of chronic renal failure, but brown tumour has a rare incidence in those patients.1 It is composed of fibrous stroma associated with multinucleated giant cells. The commonly affected sites are the long bones, ribs and facial bones, extensive osteolytic destructions are extremely rare.2 It can simulate a malignancy on clinical examination.3 This case reported just a single osteolytic lesion located in the distal femur, which was misdiagnosed as osteosarcoma. The definitive diagnosis depends on pathological examination.