This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Pathology
[{'content': 'Which of the following markers is specific for gastrointestinal stromal tumor (GIST): \nSelect and explain. \nA. CD 117, B. CD 34, C. CD123, D. S-100', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) CD 117(Ref: Robbins 9th/pg 775; 8th/pg 789)Most useful diagnostic marker is c-kit (CD117) detectable in 95% of the patients.', 'role': 'assistant'}]