[A case of metastatic lung tumor from an occult thyroid oncocytic carcinoma growing into the bronchial lumen].

We report a case of a metastatic lung tumor from an occult thyroid oncocytic carcinoma, growing into the bronchial lumen. A 70-year-old woman was referred to our hospital because of abnormal shadows which had been increasing in size for 4 years, in the chest radiograph. Bronchoscopy revealed an endobronchial tumor at the orifice of the left B4b. Histological and immunohistological examination of the lesion showed tumor cells with immunoreactivity for thyroglobulin, and a metastatic oncocytic carcinoma from the thyroid was diagnosed. Closer examination of the neck revealed thyroid carcinoma, and total thyroidectomy was performed. Endobronchial metastasis of thyroid oncocytic carcinoma is very rare. In this case, immunohistological examination was useful for detecting the primary site.