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 a highly sensitive marker for carcinoma? \nSelect and explain. \nA. Cytokeratin, B. Vimentin, C. CD45, D. Calretinin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Essentially all cells of epithelial origin express cytokeratins, which are therefore highly sensitive markers for carcinomas. Ref: Encyclopedia of Cancer, Volume 1 edited by Manfred Schwab, 2008, Page 1496', 'role': 'assistant'}]