Papillary Thyroid Carcinoma with Retropharyngeal Node Metastasis Demonstrating Negative I-131 but Positive FDG Uptake on PET/CT

Papillary Thyroid Carcinoma with Retropharyngeal Node Metastasis Demonstrating Negative I-131 but Positive FDG Uptake on PET/CT

Papillary thyroid carcinoma (PTC) is commonly accompanied by cervical lymph nodemetastasis, whereas metastases to the retropharyngeal lymph nodes (RPN) are rare.Radioactive iodine (RAI) ablation is recommended for detection and treatment ofdifferentiated thyroid carcinoma (DTC). However, in some cases of iodine-negative DTC,F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography(PET/CT) can aid in detection of additional lesions. We report on a patient with PTC whohad retropharyngeal node involvement with iodine-negative features and lowthyroglobulin level at the time of diagnosis but with metastasis identified on FDG PET/CT.