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: Surgery
[{'content': 'On the mammogram, all of the following are the features of a malignant tumor except: \nSelect and explain. \nA. Speculation, B. Microcalcification, C. Macrocalcification, D. Irregular mass', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]