A 58-year-old woman presented with an abnormal shadow on the left hilum of chest computed tomography (CP) on her first annual check. A diagnosis by a transbronchial aspiration biopsy led to the suspicion that it was a malignant mesothelioma. This seemed possible because the tumor cells with nuclear pleomorphism were positive for the immunostain of calretinin and vimentin. The PET-CT scan showed the acceleration of glucose uptake only in the left hilar lesion. We diagnosed her primary malignant hilar lung tumor of clinical staging T3N1M0, Stage IIIA. She received a left pneumonectomy. The resected lesion was the left hilar lymph node. There were no melanotic granules contained in the malignant cells, those were immunohistochemically positive for Melan-A and S-100, but negative for HMB-45. Although systemic examinations were thoroughly performed, we could detect no primary lesion. Consequently the final diagnosis was lymph node metastasis of an amelanotic malignant melanoma from an unknown primary.