Giant Cell Tumor with Secondary Aneurysmal Bone Cyst Shows Heterogeneous Metabolic Pattern on ¹⁸F-FDG PET/CT: A Case Report

Giant cell tumor (GCT) is a generally benign bone tumor accounting for approximately 5 % of all primary bone neoplasms. Cystic components in GCTs that indicate secondary aneurysmal bone cysts (ABCs) are reported in 14 % of GCTs. Although both of them have been described separately in previous reports that may show considerable fluorodeoxyglucose (FDG) uptake despite their benign nature, the findings of GCT with secondary ABC on ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) have not been well-known. We report a case of GCT with secondary ABC in a 26-year-old woman. ¹⁸F-FDG PET/CT revealed a heterogeneous hypermetabolic lesion in the left proximal femur with the maximum standardized uptake value of 4.7. The solid components of the tumor showed higher FDG uptake than the cystic components. These observations suggest that the ABC components in GCTs show heterogeneous metabolic patterns on ¹⁸F-FDG PET/CT.