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: Medicine
[{'content': 'Which of the following tumor is most commonly associated with superior vena cava syndrome? \nSelect and explain. \nA. Lymphoma, B. Small cell carcinoma, C. Non small cell carcinoma, D. Metastasis', 'role': 'user'}, {'content': "Answer: B \nExplanation: Malignant tumors such as lung cancer, lymphoma and metastatic tumors are responsible for 90% of SVCS cases. Lung cancer paicularly, small cell and squamous cell histologies account for approx 85% of all cases of malignant origin. Ref: Harrison's 16th Edition, Page 575", 'role': 'assistant'}]