Superior vena cava syndrome is caused by obstruction of blood flow in the superior vena cava, most commonly due to lung cancer compressing the vein. It presents with facial swelling, cough, difficulty breathing, and fullness in the arms. On physical exam, enlarged neck and chest veins are seen. Diagnosis is made through imaging and labs. Treatment depends on the cause, with cancer typically requiring chemotherapy, radiation or surgery to relieve pressure on the vein.