Abstract
We report an extremely rare case of malignant melanoma of the lung. A tumor-like shadow was detected in the left lung of a 48-year-old man by chest X-ray examination, Chest CT revealed a tumorous lesion with multiple small nodules around it. In addition, bronchoscopy showed a dark brown tumor that obstructed the lumen of left bronchus B4, and transbronchial lung biopsy (TBLB) was performed. A histopathological examination of a biopsy specimen showed tumor cells with large round or oval nuclei possessing characteristic basophilic nucleoli and notable variation in the amount of melanin pigments from cell to cell. The tumor cells were positive for S-100, HMB45 and vimentin but negative for keratin, EMA and LCA in immunohistochemical examinations. By these findings, the tumor was histopathologically diagnosed as a malignant melanoma. There were no tumorous lesions in other organs that might be suspected to be primary malignant melanoma although metastatic lesions were observed in the liver by CT. We conclude that these clinical and histopathological examinations indicate that this case was a very rare malignant melanoma that originated in the lung.
