Metastatic Mimicker in Thyroid Cancer with Thyroglobulin Elevation and an FDG-Avid Recurrent Aneurysmal Bone Cyst.

Many benign bone lesions mimic skeletal metastases from thyroid cancer on imaging and even may have high metabolic uptake on 18F-FDG PET/CT. It becomes crucial to distinguish these hypermetabolic lesions (benign vs. metastasis), especially in patients with thyroglobulin elevation and negative iodine scan. The index case describes a patient with thyroid cancer having thyroglobulin elevation and negative iodine scan with a hypermetabolic aneurysmal bone cyst mimicking skeletal metastasis.