Hypervascular but Metabolically Inactive Brown Tumours’: Novel Insights into Parathyroid Imaging with ⁶⁸ Ga RGD PET/CT

We report a case of a middle-aged woman who initially presented elsewhere with left elbow pain, whose initial MRI revealed an expansile lytic lesion in the proximal ulna. The first biopsy report done was misinterpreted as a giant cell tumour. Upon referral to our centre, further evaluation established the diagnosis of brown tumour secondary to primary hyperparathyroidism. Notably, while the Tc- ⁹⁹ m Sestamibi scan showed uptake at the site of parathyroid adenoma, it failed to show uptake in the bone lesions, while ⁶⁸ Ga RGD PET/CT revealed uptake in the multiple sites of brown tumours, suggesting a unique pattern of metabolic inactivity but persistent vascularity in the bone lesions. This case demonstrates the interplay of different biological pathways unlocked by advanced nuclear imaging in detecting brown tumours based on their evolving biological behaviour.