Most common anterior mediastinal tumour?

The designation "thymoma" is restricted to tumors of thymic epithelial cells. Such tumors typically also contain benign immature T cells. The tumors usually occur in adults older than 40 years of age; thymomas are rare in children. Males and females are affected equally. Most arise in the anterior superior mediastinum, but sometimes they occur in the neck, thyroid, pulmonary hilus, or elsewhere.