Thymomas, lymphomas, and germ cell tumors are the most frequent lesions of the anterior mediastinum, whereas endodermal (bronchogenic) cysts and lymphomas are the most frequent lesions of the middle mediastinum. In the posterior mediastinum, neurogenic tumors and soft-tissue sarcomas are the most frequent. Depending on tumor location, mediastinoscopy, mediastinotomy, and thoracoscopy are the preferred diagnostic methods. Surgical treatment of thymoma is the gold standard, and median sternotomy is the most frequently applied approach. The decisive prognostic and therapeutic criteria are Masaoka staging, WHO classification, and R0 status. Thoracoscopy should be performed only in patients with myasthenia gravis and with very small tumors. Surgical treatment is highly recommended in patients with locally recurrent tumors. The importance of surgical treatment of germ cell tumors is determined by a negative concentration of beta-HCG and alpha-fetoprotein and in cases of residual tumor after chemotherapy. Bronchogenic cysts always require resection because of their high complication rate (66%) after conservative treatment. In these cases complete resection is necessary due to the probability of recurrence. Ninety-eight percent of neurogenic tumors in adults are benign and usually resected via thoracoscopy or thoracotomy, depending on location and size.
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