Superior vena cava syndrome is a clinical group of syndromes in which various etiologies cause complete or incomplete obstruction of the superior vena cava, resulting in obstruction of blood return, leading to edema of the upper extremities, neck, face and superficial varicose veins of the upper body. The superior vena cava is the largest reflux vein in the upper body, through which blood from the skull and upper extremities returns to the heart. In previous decades, half of the patients with superior vena cava syndrome were caused by tuberculosis or syphilis, but in recent decades, with the widespread use of anti-TB drugs and antibiotics, the number of benign diseases causing superior vena cava syndrome is decreasing, replaced by malignant tumors, nearly 80% of which are caused by lung cancer. The superior vena cava is located in the sternum. The superior vena cava is located at the back of the sternum, to the right of the body. Lung cancer can directly invade the superior vena cava, or the lymph nodes of metastasis can increase and squeeze the superior vena cava, if the blockage is formed slowly, the surrounding veins will form compensatory hyperplasia.