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 among the following is marker of carcinoma? \nSelect and explain. \nA. Cytokeratin, B. Vimentin, C. Calretinin, D. CD 45', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cytokeratin is present in abundance in epithelial cells. Hence it serves as a useful marker of carcinoma.', 'role': 'assistant'}]