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': 'Best marker for GIST is \nSelect and explain. \nA. CD117, B. DOG 1, C. CD 34, D. CD 43', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Diagnostic markers GISTs and cajal cells express c-KIT (also known as CD117) and CD34. Most useful diagnostic marker is c-KIT and immunohistochemically detected in 95% of gastric GISTs GENERAL AND SYSTEMIC PATHOLOGY RAMDAS NAYAK FIRST EDITION PAGE 390', 'role': 'assistant'}]