[A case of lung cancer with hyperthyroidism].

We here report a case of metastasis from lung cancer to the thyroid. On presentation, this patient showed painful anterior cervical swelling and right supraclavicular lymph node swelling. Laboratory data showed primary hyperthyroidism. Although subacute thyroiditis was suspected, echo-guided needle aspiration biopsy and lymph node biopsy revealed poorly differentiated squamous cell carcinoma. As a result, primary lung cancer with thyroid metastasis was diagnosed based on mediastinal enlargement on chest X ray films and normal findings in organs other than the lung and thyroid. Chemotherapy for lung cancer induced a decrease in the size of tumor and the normalization of thyroid function. However, 2 months after the normalization, cervical swelling enlarged and a lung mass in right upper lobe and skin tumor appeared. Despite treatment with chemotherapy, she died. Postmortem revealed that the right upper lung carcinoma was the primary lesion and immunohistochemical staining for surfactant protein was positive in the thyroid, skin tumor and lymph node, which revealed these carcinomas had metastasized from lung cancer. To the best of our knowledge, thyrotoxicosis induced by thyroid metastasis of lung cancer is an uncommon case.