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
Superior vena cava syndrome is caused most commonly by - 
Select and explain. 
A. Adenocarcinoma, B. Squamous cell carcinoma, C. Small cell carcinoma, D. Large cell carcinoma
C: Small cell carcinoma
Answer: C: Small cell carcinoma 
Explanation: "Superior vena cava syndrome results from obstruction of the superior vena cava by central upper lobe tumors, usually the small cell tumors" - Cecil, 5/e, p 1207 (Cecil is a standard text book of Medicine by Saunders publication) "Superior vena cava (SVC) syndrome most frequently occurs with small-cell carcinoma, with bulkly enlargement of involved mediastinal lymph nodes and compression of the SVC." - Schwartz 9/e