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
[{'content': 'Which of the following markers is specific for gastro-intestinal stromal tumor (GIST) - \nSelect and explain. \nA. CD117, B. CD34, C. CD23, D. S-100', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Immunohistochemistry\n\nFollowing markers are present in GISTs:\n\n\nCD 117 (c kit) →\xa095%\nCD 34\xa0→ 70%\nSmooth muscle actin\xa0→ 5%\n\n\nCD 117 (c kit) is considered the most specific marker\nCD 117 (c kit) immunoreactivity is the best defining feature of GISTs distinguishing them from true smooth muscle tumors (leiomyoma) and tumors arising from neural crest.\nAlthough CD 117 (c kit) is considered the most specific marker for GIST, it is not pathognomonic of GIST as other tumors may also express CD 117. These tumors include mast cell tumor, germ cell tumors (seminomas), leukemias, malignant melanoma, angiolipomas, and some sarcomas.', 'role': 'assistant'}]