A Patient Presented with Extensive Lung Metastases of Papillary Thyroid Carcinoma Without Any Primary Focus Detected on Total Thyroidectomy

The most common metastatic sites of differentiated thyroid cancer (DTC) are the lung and bone after lymph nodes. A newly defined type of occult DTC is consistent with metastatic disease without an identified primary malignancy in the thyroid gland after total resection. We present a patient with multiple lung metastases of occult DTC showing mild 18F-fluorodeoxyglucose (FDG) uptake and intense radioiodine uptake without a primary lesion in the thyroid gland.