A 63-yrs-old man is having facial swellingWhat condition is the most likely cause of these findings?

Superior vena cava obstruction is almost always due to malignancy and, in three out of four cases, results from invasion of the vena cava by bronchogenic carcinoma. Lymphomas account for most of the remaining cases of the superior vena cava syndrome Fibrosing mediastinitis as a complication of histoplasmosis or ingestion of methysergide may occur but is rare.' Rarely a substernal thyroid or thoracic aortic aneurysm may be responsible for the obstruction. Although constrictive pericarditis may decrease venous return to the heart, it does not produce obstruction of the superior vena cava. Whatever the cause of the superior vena cava syndrome, the resultant increased venous pressure produces edema of the upper body, cyanosis, dilated subcutaneous collateral vessels in the chest, and headache. Cervical lymphadenopathy may also be present as a result of either stasis or metastatic involvement, When carcinoma is the cause of the superior vena cava syndrome, the treatment is usually palliative and consists of diuretics and radiation.