Abstract
Thyroid metastases from lung cancer are very rare. A woman aged 42 years with a tumour in the lower lobe of the right lung was diagnosed as having lung adenocarcinoma positive for echinoderm microtubule-associated proteinlike 4-anaplastic lymphoma kinase. Positron emission tomography demonstrated fluorodeoxyglucose accumulation in the lower lobe of the right lung, the right thyroid lobe and both adrenal glands. We performed fine-needle aspiration biopsy (FNAB) and used reverse transcriptase-PCR (RT-PCR) to diagnose the patient as having metastatic lung adenocarcinoma to the thyroid gland. We believe that FNAB combined with RT-PCR can be an effective method for diagnosing metastatic lung adenocarcinoma to the thyroid gland.