SAT-338 An Unusual Case of Brown Tumor in the Left Femur Associated with Secondary Hyperparathyroidism

Abstract

Background: Brown tumor of hyperparathyroidism (BTHPT) are non-neoplastic bony lesions that arise from increased osteoclastic activity in the setting of uncontrolled hyperparathyroidism, (HPT). The prevalence is low, with a frequency of 3% in primary HPT and 2% in secondary HPT. It is rare as earlier detection and treatment of HPT prevents the progression and development of BTHPT. BTHPT is more common when HPT is untreated. BTHPT are benign tumors which usually show high 18Fludeoxyglucose-PET/CT (FDG) uptake. The mechanism of elevated FDG uptake has been suggested to be the presence of giant cells, and intracellular glucose metabolism of the macrophages may also play a role. We describe a case of a patient who presents with FDG uptake-negative BTHPT of the left femur. Clinical Case: 62-year-old male with end-stage renal disease (ESRD) and secondary HPT presented with severe left hip pain for many months. The patient had poor access to health care and had not received routine medical treatments at an outside facility prior to presentation at our facility. Laboratory studies showed PTH 1942 pg/ml (14–72), Calcium 8.7 ng/dl (8.4–10.2), phosphorus 3.6 mg/dl (2.5–4.9), Vitamin D total 19.7 ng/ml (30–140), Vit D 1,25 9 pg/ml (18–72), and creatinine 7.75 mg/dl (.66-1.28), alkaline phosphatase 57 u/L (33–94). FDG scan revealed several lucencies in the left proximal femur, with no uptake. The patient underwent left total hip arthroplasty due to impending pathological fracture. Surgical pathology revealed fragments of fibrous tissue with fibroblasts, hemosiderin and interstitial hemorrhage, consistent with brown tumor. Conclusion: We describe a unique case of BTHPT of the left femur which was the unrecognized cause of hip pain. BTHPT occurs late in the setting of HPT and is considered as a sign of poorly controlled disease. This is the first case of BTHPT to our knowledge that is not FDG-avid. This is unusual given the vascularity seen in these tumors and highlights that glucose utilization may not necessarily reflect the degree of osteoclastic activity in these tumors. Medical treatment has been shown to be sufficient in helping resolve these lesions, although the process is usually slow. Conversely, in cases of refractory disease, subtotal parathyroidectomy may be required. Our case describes an FDG-negative BTHPT, and highlights that although rare, this should be considered in the management of patients with ESRD, secondary HPT and hip pain. Patients can present with various imaging characteristics. Despite being rare, this case underscores the importance of recognition of BTHPT, so that intervention may be rendered early.