[Metastatic Lung Tumor from Papillary Thyroid Carcinoma Suspected of Primary Lung Cancer;Report of Two Cases].

Radiological finding of pulmonary metastasis of thyroid cancer is generally known to be multiple small nodular shadow. We experienced 2 cases of lung solitary tumor, which were suspected of primary lung cancer as differential diagnosis. Patient 1:A 67-year-old man;the tumor obstructed subsegmental bronchus (B10) of the right lobe, and pathological diagnosis by transbronchial biopsy was adeno-squamous carcinoma. Fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) showed abnormal uptake in the tumor and also in the left lobe of his thyroid gland, but no malignant findings were found by the fine-needle aspiration cytology from the thyroid gland. Patient 2:A 51-year-old woman;she had a lobulated nodule in the left lower lobe, which was diagnosed as adenocarcinoma. She had undergone an operation for thyroid cancer about 30 years earlier, but after the operation, there has been no recurrence. In both cases, primary lung cancer were suspected and the tumors were resected surgically. By immunohistochemistry, both tumors were diagnosed as pulmonary metastases from papillary thyroid carcinoma.