Thymoma. The most common anterior mediastinal mass

Thymomas may be discovered during routine evaluation, through reported symptoms, or increasingly, during evaluation for myasthenia gravis. Histologic details of these tumors have little bearing on prognosis or evaluation of malignant potential. Malignancy is determined by evidence of invasion through the tumor capsule at surgery or of distant spread. Complete surgical excision is the mainstay of therapy for both benign and malignant thymoma. Biopsy of anterior mediastinal masses via mediastinoscopy should be avoided because of the risk of violating the thymoma capsule. If the capsule is surgically violated or extracapsular invasion is present, postoperative radiation therapy is indicated.