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: Pathology
Which of the following is a specific marker for ewings sarcoma? 
Select and explain. 
A. CD 45, B. CD 99, C. HMB-45, D. CD1a
B: CD 99
Answer: B: CD 99 
Explanation: CD 99 (MIC 2 ) is a specific marker for ewings sarcoma