The middle mediastinum contains the heart, lungs, thymus, great vessels, and mediastinal lymph nodes, among other structures. Some masses in this area include:
1. Lymphoma: A type of cancer that starts in the lymph node cells.
2. Thyroid cancer: A rare form of cancer that starts in the thyroid gland.
3. Mediastinal teratoma: A rare type of tumor that contains various tissues such as hair, teeth, cartilage, etc.
4. Thymoma: A tumor that starts in the thymus gland.
5. Aneurysm: A bulge or dilation in an artery that can rupture and cause internal bleeding.
