A Case of Minimal Thyroid Carcinoma Diagnosed by a Solitary Pulmonary Metastasis

We report a case of minimal thyroid carcinoma diagnosed by a solitary pulmonary metastasis. A 70's man visited a medical practitioner because of chest discomfort, and there was an abnormality on the chest X-ray. Chest computed tomography(CT) showed a nodule in the right middle lobe of the lung. Positron emission tomography with 18-fluorodeoxyglucose(FDG)-PET revealed increased FDG uptake in that tumor, but did not reveal any other lesion. The tumor was clinically suspected to be a carcinoid tumor, primary lung cancer, metastatic lung cancer, or a benign tumor. Right middle lobe lobectomy was performed, and the tumor was diagnosed as a metastasis from a thyroid papillary carcinoma by pathological diagnosis during surgery. After surgery, we found a tumor in the left lobe of the thyroid by CT and US. Because the patient did not desire 131I therapy, he underwent a left hemithyroidectomy and neck dissection. There was a papillary carcinoma 1.0 cm in the thyroid gland and there were 3 cervical lymph node metastases. There has been no recurrence for 11 years after surgery.