Causes of Superior Vena Cava Syndrome
Malignancy accounts for the vast majority of SVC syndrome cases, with lung cancer responsible for 72% of all cases (50% non-small cell lung cancer and 22% small cell lung cancer). 1
Malignant Causes
Primary Malignancies
- Lung cancer is the dominant cause, representing approximately 72% of all SVC syndrome cases 1
- Non-Hodgkin lymphoma is the second most common malignancy causing SVC syndrome 2
- Other thoracic malignancies including mediastinal tumors 2, 3
Mechanism of Malignant Obstruction
The malignancy causes SVC syndrome through three distinct mechanisms 3, 4:
- External compression of the SVC by tumor mass in the right lung, mediastinal lymph nodes, or other mediastinal structures 1
- Direct neoplastic invasion of the SVC vessel wall 3
- Internal obstruction with tumor thrombus or bland thrombus 3
Benign Causes
Benign etiologies are increasingly common due to the rising use of intravascular devices. 2, 5
Thrombotic Causes
- Central venous catheter-related thrombosis is the most common benign cause 2, 5
- Pacemaker or defibrillator lead-associated thrombosis 2, 5
- Thrombosis within the SVC from any indwelling device 1
Other Benign Causes
Clinical Context
In approximately 60% of cases, SVC obstruction is the presenting symptom that leads to the diagnosis of lung cancer. 1 This underscores the importance of obtaining histologic diagnosis before initiating treatment, as the underlying cause fundamentally determines management strategy—chemotherapy for SCLC versus radiation therapy and/or stenting for NSCLC. 1, 6
The pathophysiology involves obstruction forcing blood through smaller collateral vessels to the azygos vein or inferior vena cava, with venous collaterals dilating over several weeks. 1 Upper body venous pressure is markedly elevated initially but decreases over time as collaterals develop. 1