Endocrine Abstracts

Background: Brown tumor of bone is a non-neoplastic lesion resulting from abnormal bone metabolism in hyperparathyroidism. Brown tumor, as the only and initial symptom of normocalcemic primary hyperparathyroidism is extremely rare.

Case presentation: A 69-year-old female patient was admitted to the hospital with a mass in the right thigh. A mass lesion of the right distal femur with bone and soft tissue infiltration was observed in the lower extremity magnetic resonance imaging (MRI). The size of the mass was measured as approximately 10×3.7×4.6 cm. Apart from this lesion, nodular lesions were detected in various dimensions on the right femur, left femur and left patella. Brown tumor was detected in pathologic evaluation of the mass of the right distal femur. The patient was examined for hyperparathyroidism. Serum parathormone (PTH) level was 2698 pg/mL (reference range 15–68), calcium level was 8.8 mg/dL (8.4–10.2), phosphorus level was 2 mg/dL (2.4–4.4) and 25-OH D level was 10 μg/L. Vitamine D treatment was given to the patient. 24-hour urine calcium could not be assessed because of the patient’s low compliance. The total lomber T score was −4.7 and the femur neck T score was −5.5 in the bone mineral density. Localization studies were performed and neck ultrasonography and parathyroid scintigraphy revealed a parathyroid adenoma in the inferior right lobe. Patient underwent parathyroidectomy surgery and in histopathological evaluation solitary parathyroid adenoma was observed. The follow-up of the patient whose postoperative PTH decreased to 161 pg/mL is being continued.

Discussion: Cytologically, it is difficult to separate the brown tumor from any other giant cell lesions. To prevent unnecessary surgical procedures, PTH assay is necessary in any patient with expansive lytic lesion of the bone, even if serum calcium level is normal.