To diagnose thymoma in a case of mediastinal mass is:

Once a mediastinal mass is detected, Next step: 1. Initial mediastinoscopy or limited thoracotomy to get sufficient tissue to make an accurate diagnosis. 2. Fine-needle aspiration is poor at distinguishing between lymphomas and thymomas 3. Subsequent staging of thymoma can be done with chest CT scans 4. MRI has a defined role in the staging of posterior mediastinal tumors 5. Somatostatin receptor imaging with indium-labeled somatostatin analogues also used for staging Ref: Harrison, E-18, chapter e-20.