<prompt> Which of the following carcinomas most frequently metastasizes to brainSmall cell carcinoma of lungProstate cancerRectal carcinomaEndometrial cancer  <response>: 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 Hodgkins disease rarely metastasizes to brain. Ref: Harrison I7e 