<prompt> The commonest anterior mediastinal tumour isAneurysm of descending aoaNeurogenic tumourThymomaBronchogenic cyst  <response>: Thymomas are the most common anterosuperior mediastinal tumors accounting for 25 of the total.They are commonly associated with myasthenia gravis.Diagnosis and treatment is best achieved by complete thymectomy. Reference:SRBs manual of surgery,5th edition,page no:1127. 