A 60-year-old male presented to the emergency with breathlessness, facial swelling and dilated veins on the chest wall. The most common cause is:

Superior vena caval syndrome:symptomssignsswelling around neck and face especially around eyesdyspneacoughhoarseness, headache, tongue swelling, nasal congestion, epistaxis, haemoptysis, dysphagia, pain, dizziness, syncopedilated neck veinsincreased number of collateral veins over the anterior chest wallcyanosisoedema of face, arms, and chestproptosis, glossal & laryngeal oedema and obtundation in severe casesSymptoms are aggravated by bending forwards and lying downLung cancer is the commonest cause of SVC obstruction(ref: Harrison's 18/e p2266, 17/e p1730)