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: Radiology
[{'content': 'Which of the following is not a characteristic of malignant lesions? \nSelect and explain. \nA. Pear-shaped, B. Ulcerated borders, C. Ill-defined borders, D. Absence of encapsulation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The periphery most often is ill defined and has an invasive characteristic commonly seen in malignant tumors.\nThe imaging presentation of malignant tumors\xa0is variable and is related to the grade, aggressiveness, location, and type of tumor. In many cases, it is impossible to determine whether a tumor\xa0 is malignant or benign. However, features such as ill-defined margins, invasion of adjacent soft tissues (e.g., fat spaces), and destruction of adjacent osseous structures are considered to be typical\xa0 indicators\xa0of malignancy.\nOral radiology White and Pharaoh; 7th ed. Page no 557', 'role': 'assistant'}]