Brown Tumors Secondary to Parathyroid Carcinoma Masquerading as Skeletal Metastases on 18F-FDG PET/CT: A Case Report

ABSTRACT Objective Brown tumors develop as skeletal manifestations of hyperparathyroidism. Increased osteoclast activity leads to accumulation of highly active giant cells and to excess cortical bone resorption, producing fibrous cysts. Though most often reported in patients with parathyroid adenomas, brown tumors secondary to parathyroid carcinoma create a clinical dilemma. Increased signal uptake on 2-deoxy-2-(fluorine-18)fluoro-D-glucose positron emission tomography (18F-FDG PET)/computed tomography (CT) seen within brown tumors may be indistinguishable from bone metastases. We report a case of parathyroid carcinoma in a 38-year-old man presenting with osteolytic bone lesions on 18F-FDG PET/CT that were diagnosed as brown tumors by biopsy. Methods We describe the patient history, presentation, diagnostic studies, and treatment. Results We report a case of a 38-year-old man diagnosed with parathyroid carcinoma with associated hypercalcemia and elevated parathyroid hormone levels who had undergone 3 surgical resections for local recurrences and had persistent hypercalcemia. He was found to have multiple osteolytic lesions throughout his skeleton on 18F-FDG PET/CT imaging 2 months after diagnosis. Biopsy of a right scapula lesion confirmed a brown tumor. Conclusion The role of 18F-FDG PET/CT in management of parathyroid carcinoma has not been systematically evaluated. Skeletal manifestations of parathyroid carcinoma may be present in this imaging modality. Clinicians should consider the possibility of brown tumors in patients with parathyroid carcinoma who undergo 18F-FDG PET/CT imaging.