Mediastinal tumors develop in the mediastinum — that area of the chest that separates the lungs and contains the heart, aorta, esophagus, thymus, and trachea. Depending on the specific type of cells involved, these rare tumors can develop in epithelial, connective, nerve and muscle tissue, and demand careful evaluation and specialized expertise for an accurate diagnosis.
The mediastinum is divided into three sections:
Anteriorsuperior – Both in front and high, toward the head (Common tumors: thymoma, lymphoma, germ cell)
Middle – Also known as visceral, containing the chest organs (Common tumors: benign cysts)
Posterior – Also known as paravertebral, running along the spine in the back (Common tumors: neurogenic)
Mediastinal tumors can be benign (non-cancerous) or malignant (cancerous). Most mediastinal tumors in adults occur in the anterior mediastinum and are usually lymphomas or malignant thymomas. These tumors are most common in individuals between 30 and 50 years of age.
Types of Mediastinal Tumors
The thymus is a gland located behind the breastbone. Part of the immune system, this gland produces white blood cells called T-lymphocytes, which help protect the body from infection. (If lymphocytes become cancerous, they can develop into lymphoma.) There are three major types of mediastinal tumors involving the thymus gland:
Thymomas - Tumors that develop on the surface of the thymus gland. These types of tumors have been linked to autoimmune conditions such as myasthenia gravis, rheumatoid arthritis and lupus erythematosus.
Thymic carcinoma (also called type C thymoma) - An aggressive cancer that usually spreads quickly and has a high risk of recurrence. Thymic carcinoma is divided into subtypes, depending on the types of cells in which the cancer began.
Thymic carcinoids - Neuroendocrine cancers that account for 2 percent of all mediastinal tumors and 5 percent of thymic cancers.
Lymphomas - Cancers of the lymph glands that can develop in the mediastinum either as the primary cancer or as part of more widespread disease.
Neurogenic tumors begin in cells that make up the nervous system and represent about 20-25 percent of all mediastinal tumors. In adults, most of these tumors are non-cancerous and successfully treated by surgery. A schwannoma, which originates from the Schwann cells in the peripheral nervous system, is an example of a neurogenic tumor. Most schwannomas are benign and asymptomatic, but signs of nerve compression and paralysis, Pancoast syndrome, and Horner's syndrome can occur.
Germ cell tumors form from embryologically immature cells. Most germ cell tumors will form in the sex organs (e.g., the testes), but they can develop anywhere in the body, including the mediastinum.
Mesenchymal tumors develop from mesenchymal cells in the connective tissue. A sarcoma is a cancer of the mesenchymal cells.
About half of all patients with mediastinal tumors will experience no symptoms. When symptoms do occur, they are often the result of compression to the nerves and other structures and could be an indication of cancer. General symptoms, which are sometimes mistakenly attributed to a cold or flu, include shortness of breath, cough, fever, chills, night sweats, unexplained weight loss, swollen lymph nodes and hoarseness. If symptoms persist for more than two weeks, see your doctor.