Refractory Chylothorax in Primary Mediastinal Large B-Cell Lymphoma: A Case of Superior Vena Cava Obstruction Thrombosis-Induced Lymphatic Leak Salvaged by Mechanical Thrombectomy.

Chylothorax is an uncommon presentation of mediastinal lymphoma, typically attributed to direct tumour invasion. This case illustrates a rare mechanism of superior vena cava (SVC) thrombosis and venolymphatic hypertension, leading to refractory chylothorax. A 33-year-old man with primary mediastinal large B-cell lymphoma presented with dyspnoea and right-sided pleural effusion. He was diagnosed with chylothorax. Lymphangiography revealed lymphatic leak secondary to thrombosis involving the venolymphatic junction. Despite conservative management including repeated thoracentesis, talc pleurodesis, total parenteral nutrition and anticoagulation, the chyle leak persisted. Mechanical thrombectomy was performed, successfully restoring flow in the brachiocephalic veins and SVC. The chylothorax resolved completely afterwards, allowing the chest drain to be removed. This case highlights venous thrombosis as a possible cause of refractory chylothorax. When systemic anticoagulation fails, mechanical thrombectomy is a definitive, causality-driven treatment.