摘要Objective? A typical brown tumor caused by hyperparathyroidism (HPT) is rare. In this report, we describe our pathological findings along with a review of the literature to enhance understanding of the disease and prevent misdiagnosis, as well as to provide evidence for treatment and prognosis. Methods? We present a case of brown tumor of the left proximal femur and pelvis in a 57-year-old woman who was admitted to our hospital (Dalian Municipal Central Hospital, Dalian, China). Pelvic computed tomography (CT) showed cystic expansile lesions in the left proximal femur and pelvis. Lung and abdominal CT also revealed multiple lytic lesions in the ribs and lumbar spine. X-ray of the left ulna and radius showed that the middle of the left ulna had a fracture caused by a brown tumor. A bone biopsy from the left proximal femur showed focal distribution of giant cells, with hemorrhage and fibrin hyperplasia. Results? The patient underwent internal fixation of the left intertrochanteric fracture, and postoperative bone biopsy showed focal distribution of giant cells with hemorrhage and fibrin hyperplasia. The patient had a parathyroidectomy 5 months after discharge. Two weeks later, the patient developed a fracture in the right femoral neck and pain in the left forearm. X-ray of the left ulna and radius showed that the middle of the left ulna was affected by a pathological fracture caused by a brown tumor. The patient was debilitated and declined surgical treatment. The patient and her family chose discharge. Conclusion? Brown tumor of bone, also called osteitis fibrosa cystica, is a rare non-neoplastic lesion that reflects abnormal bone metabolism in patients with HPT. However, with fine needle aspiration cytology in combination with biochemical tests, a correct diagnosis can be reached. The increase in osteoclast activity leads to decalcification and dissolution of bone, and formation of a cystic bone defect with hyperplastic fibrous tissue. This eventually becomes a brown tumor, with deformed and bleeding fibrous tissue. The patient had a typical brown tumor, as well as osteoporosis, anemia, and pathological fractures.