Detection of Unexpected Brown Tumors Due to Hyperparathyroidism Diagnosed by 18F-FDG PET/CT.

A 27-year-old man was called to receive a kidney transplant. The preoperative CT of the chest showed multiple osteolytic lesions, as well as a hypodense structure posterior in the right thyroid lobe. Blood analysis showed elevated parathyroid hormone, phosphorus, and alkaline phosphatase levels, with normal calcium and 25-OH-vitamin D. F-FDG PET/CT demonstrated generalized elevated FDG uptake in the bone (due to hyperparathyroidism), as well as multiple hypermetabolic focal lesions spread throughout the bone (fitting brown tumors). The nodule posterior of the right thyroid lobe showed an intense FDG uptake as well, suggestive of a parathyroid adenoma/hyperplasia. Histopathology confirmed the diagnosis.