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
Which of the following carcinomas most frequently metastasizes to brain 
Select and explain. 
A. Small cell carcinoma of lung, B. Prostate cancer, C. Rectal carcinoma, D. Endometrial cancer
A: Small cell carcinoma of lung
Answer: A: Small cell carcinoma of lung 
Explanation: Ans. is 'a' i.e. small cell Ca of lung Because of its high blood flow brain is a common site for metastasis. Primary sites in decreasing order are : Lung > breast > melanoma > kidney Prostate Ca, ovarian cancer and Hodgkin's disease rarely metastasizes to brain. (Ref: Harrison I7/e)