Osteitis fibrosa cystica mistaken for malignant disease.

A 65-year-old man with back pain had plain radiographs that showed multiple osteolytic bone lesions of the pelvis, femur and L-spine; an magnetic resonance imaging scan of the L-spine showed extensive bony resorption with a posterior epidural mass involving the L1 spinous process; these findings suggested multiple myeloma or bony metastasis. However, all serology testing was negative. The parathyroid hormone and serum calcium levels were found to be abnormally elevated. A fine needle aspiration biopsy suggested that the L-spine lesion was consistent with the diagnosis of osteitis fibrosa cystica. A pathological fracture of the spine compressed the spinal cord, and surgical intervention was required. The neck computed tomography and Tc-99m sestamibi scan showed a solitary parathyroid mass. A minimally invasive parathyroidectomy using intraoperative parathyroid hormone monitoring was performed and two enlarged parathyroid glands identified. This case illustrates the importance of the consideration of a rare brown tumor associated with primary hyperparathyroidism in patients with the bone lesions suggestive of a malignancy.