Primary malignant melanoma of the thymus: report of a case.

A 61-year-old male was admitted to our hospital complaining of bloody sputum. A chest roentgenogram revealed a clearly demarcated mass located in the anterior mediastinum. Positron emission tomography revealed abnormal accumulation of 18F-fluorodeoxy glucose only in the anterior mediastinal tumor. A computed tomography-guided needle aspiration biopsy was performed, and the tumor was diagnosed as a malignant melanoma. Although the skin, eyeballs, oral cavity, nasal cavity, etc., were closely evaluated, no other lesion of malignant melanoma was detected except the mediastinal tumor. Hence, this tumor was diagnosed as a primary malignant melanoma. We performed total thymectomy, including the tumor, and combined resection of the adhesive bilateral lungs, pericardium and left brachiocephalic vein. Because the tumor was histologically surrounded by thymus tissue, we diagnosed it as a primary mediastinal malignant melanoma that originated in the thymus. Although the patient’s postoperative course was uneventful, he complained of back pain 5 months after the operation. Multiple bone metastases were found, and he received chemotherapy and radiotherapy, and is currently alive with disease 14 months after the primary treatment.