[Tiny Size Lung Cancer which was not Pathologically Diagnosed before Hilar and Mediastinal Dissection]

A 63-year-old man was found to have abnormally high carcinoembryonic antigen levels in a health examination. Computed tomography scan revealed lymphadenopathy at the right hilum of lung and right upper mediastinum. Malignancy was suggested by endobronchial ultrasound-guided transbronchial needle aspiration(EBUS-TBNA)for lymph node. Lymph node metastases of lung cancer was suspected, but primary site was unidentified. In order to perform complete hilar dissection, right upper lobectomy was done with systematic mediastinal dissection. Pathological diagnosis was adenocarcinoma of 3 × 3 mm in size in the fibrous scar of the right upper lobe. Immunostaining revealed thyroid transcription factor-1(TTF-1) [+]and paired box-8(PAX-8) [-] indicating the tumor to be a primary lung cancer.