Chronic mediastinitis, also known as idiopathic mediastinal fibrosis, has a complex etiology. Chronic mediastinitis can lead to superior vena cava obstruction, and patients present with a range of signs and symptoms of superior vena cava obstruction (superior vena cava syndrome (SVCS) is a group of syndromes due to the interplay of partial or complete obstruction of blood flow back to the right atrium through the superior vena cava, and it is a common oncologic emergency. Patients present with acute or subacute dyspnea and swelling of the face and neck. (Examination may reveal bruising of the neck, upper extremities, and chest, edema, which progresses to hypoxia and increased intracranial pressure, requiring urgent management). Tuberculosis, histoplasmosis, actinomycosis, tuberculosis, syphilis, post-traumatic mediastinal hemorrhage, and drug toxicity are known to cause mediastinal fibrosis. It may also be associated with autoimmunity. The etiology is unknown in some patients. The disease progresses slowly, forming dense fibrous tissue in the mediastinum in the form of sheets or hard lumps. It occurs in the upper central part of the anterior and middle mediastinum. It mainly invades the superior vena cava, the innominate vein or the singular vein, resulting in stenosis or obstruction, while other organs such as large pulmonary vessels or the esophagus, trachea, and bronchi may also be involved. In a few patients, cervical fibrosis and retroperitoneal fibrosis may occur at the same time.