Masses in the anterior portion of the mediastinum can include thymoma, lymphoma, pheochromocytoma and germ cell tumors including teratoma. Lung cancer typically spreads to the lymph nodes in the mediastinum.

Anterior mediastinal compartment, also known as anterosuperior compartment, is anterior to the pericardium. Masses in this area is more likely to be malignant than those in other compartments. Most common masses found here include thymomas, germ cell tumors, lymphomas, thyroid tissue, and parathyroid lesions.

In several editions of Physical Diagnosis, concerning mediastinal tumors the author writes:

Many signs and symptoms of a mediastinal tumor do not distinguish between these two principal classes of mediastinal tumor. However, on a radiograph usually the former class will have an irregular shape and the latter class will have a smooth spherical or ovoid shape. A large minority of patients with a mediastinal teratoma (including dermoid cyst) will cough up hair. For a differential diagnosis, the key is to exclude aneurism.