Thymoma

Thymoma is a tumor of thymic epithelial origin,and it is a common cause of anterior mediastinal mass in adults.Occasionally,these lesions arise in the middle or posterior mediastinum.It is extremely difficult to determine if thymomas are benign or malignant by histologic criteria.Local invasion at surgery is a much more reliable sign,and the terms invasive thymoma or noninvasive thymoma are preferable to malignant or benign thymoma,respec-

Thymoma is a tumor of thymic epithelial origin, and it is a common cause of anterior mediastinal mass in adults. Occasionally, these lesions arise in the middle or posterior mediastinum. It is extremely difficult to determine if thymomas are benign or malignant by histologic criteria. Local invasion at surgery is a much more reliable sign, and the terms invasive thymoma or noninvasive thymoma are preferable to malignant or benign thymoma, respectively. Approximately 30% of thymomas are pathologically and surgically invasive. Invasive of mediastinal structures or the pleural space is most typical. Distant metastases are not common with invasive thymoma.