Which of the following carcinomas most frequently metastasizes to brain
Small cell carcinoma of lung
Prostate cancer
Rectal carcinoma
Endometrial cancer
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)