This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Which is the most common metastatic disease causing SVC syndrome? \nSelect and explain. \nA. Ca Bronchus, B. Ca Breast, C. Ca Veebrae, D. Ca Stomach', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Breast cancer is the most common metastatic disease causing SVC syndrome. Lung cancer is the most common cause of SVC syndrome. Non Hodgkins lymphoma is the second most common cause. Primary mediastinal malignancies such as thymoma and germ cell tumors account for less than 2% cases.', 'role': 'assistant'}]