Brown Tumors Due to Primary Hyperparathyroidism in a Patient with Parathyroid Carcinoma Mimicking Skeletal Metastases on (18)F-FDG PET/CT

Parathyroid carcinoma only represents <1% of all cases of primary hyperparathyroidism (PHPT). Even rare, chronic PHPT may lead to excessive osteoclast activity, and the increased resorption leads to destruction of cortical bone and formation of fibrous cysts with deposits of hemosiderin—so-called brown tumors. These benign, osteolytic lesions may demonstrate FDG-avidity on (18)F-FDG PET/CT, and as such are misinterpreted as skeletal metastases. Regression of the lesions may occur following successful treatment. We present a case demonstrating the diagnostic work-up and follow-up of a patient with PHPT due to parathyroid carcinoma and with presence of brown tumors on (18)F-FDG PET/CT, visualizing the possible role of this imaging modality in the evaluation of treatment response in these patients.