Symptoms are usually relieved with radiation therapy within one month of treatment. However, even with treatment, 99% of patients die within two and a half years. This relates to the cancerous causes of SVC that are 90% of the cases. The average age of onset of disease is 54 years of age.

Superior vena cava syndrome (SVCS), is a group of symptoms caused by obstruction of the superior vena cava (a short, wide vessel carrying circulating blood into the heart). More than 90% of cases of superior vena cava obstruction (SVCO) are caused by cancer - most commonly bronchogenic carcinoma, typically a tumor outside the vessel compressing the vessel wall. It can also be caused by compression from an aortic aneurism or it can sometimes have a benign cause. Characteristic features are edema (swelling due to excess fluid) of the face and arms and development of swollen collateral veins on the front of the chest wall. Shortness of breath and coughing are quite common symptoms; difficulty swallowing is reported in 11% of cases, headache in 6% and stridor (a high-pitched wheeze) in 4%. The condition is rarely life-threatening, though edema of the epiglottis can make breathing difficult, and edema of the brain can cause reduced alertness, and in less than 5% of cases of SVCO, severe neurological symptoms or airway compromise are reported.

The mediastinum is the cavity that separates the lungs from the rest of the chest. It contains the heart, esophagus, trachea, thymus, and aorta. The mediastinum has three main parts: the anterior mediastinum (front), the middle mediastinum, and the posterior mediastinum (back).

The most common mediastinal masses are neurogenic tumors (20% of mediastinal tumors), usually found in the posterior mediastinum, followed by thymoma (15-20%) located in the anterior mediastinum.

Masses in the anterior portion of the mediastinum can include thymoma, lymphoma, pheochromocytoma, germ cell tumors including teratoma, thyroid tissue, and parathyroid lesions. Masses in this area are more likely to be malignant than those in other compartments.

Masses in the posterior portion of the mediastinum tend to be neurogenic in origin, and in adults tend to be of neural sheath origin including neurilemomas and neurofibromas.

Lung cancer typically spreads to the lymph nodes in the mediastinum.

Second most common primary anterior mediastinal mass in adults. Most are seen in the anterior compartment and rest are seen in middle compartment. Hodgkin's usually present in 40-50's with nodular sclerosing type (7), and non-Hodgkin's in all age groups. Can also be primary mediastinal B-cell lymphoma with exceptionally good prognosis. Common symptoms include fever, weight loss, night sweats, and compressive symptoms such as pain, dyspnea, wheezing, Superior vena cava syndrome, pleural effusions (10,11). Diagnosis usually by CT showing lobulated mass. Confirmation done by tissue biopsy of accompanying nodes if any, mediastinoscopy, mediastinotomy, or thoracotomy. FNA biopsy is usually not adequate. (12,13,14) Treatment of mediastinal Hodgkin's involves chemotherapy and/or radiation. 5 year survival is now around 75%. (15) Large-cell type may have somewhat better prognosis. Surgery is generally not performed because of invasive nature of tumor.

Of all cancers involving the same class of blood cell, 2% of cases are mediastinal large B cell lymphomas.