Case report- Primary hyperparathyroidism with Brown tumors masquerading skeletal metastases – Role of functional imaging in diagnosis and management

Brown tumors of bone are highly vascular, lytic bone lesions representing a reparative cellular process rather than a neoplastic process seen in patients with hyperparathyroidism. These tumors may behave aggressively and can be destructive. We present a case of 33 year old male who presented with progressively increasing swelling in right leg region. A lytic lesion involving right tibia was seen in regional CT which was suspicious for malignancy. Whole body F18-FDG PET-CT was done for further evaluation. PET-CT showed multiple sites of skeletal lesions with a large mass in right lobe of thyroid gland. Biopsy from tibial lesion revealed it to be osteoclast rich tumor raising a possibility of parathyroid mass with multiple brown tumors. Biochemical parameters revealed high Serum Calcium, Serum Total Alkaline Phosphatase and Serum parathyroid hormone (S. PTH). 99mTehnitium Sestamibi (99 m Tc MIBI) imaging was done which localized a right superior parathyroid adenoma with a suspicious right inferior parathyroid adenoma. The patient underwent right superior and inferior parathyroidectomy along with right hemithyroidectomy. Intra-operative fresh S.PTH sample was sent which dropped down to 73.4 ng/ml from 1500 ng/ml. Brown tumor is a potential cause of false-positive result in evaluation of a patient for unknown primary tumor or skeletal metastases with F18-FDG PET-CT imaging.