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': 'With regard to the malignant behavior of leimyosarcoma, the most impoant criterion is: \nSelect and explain. \nA. Blood vessel penetration by tumor cells, B. Tumor cells in lymphatic channels, C. Lymphocyte infiltration, D. The number of mitoses per high power field', 'role': 'user'}, {'content': "Answer: D \nExplanation: An impoant microscopic criterion for distinguishing leiomyosarcoma from leiomyoma is the number of mitoses present. Greater than 10 mitoses per10 high-power fields (hpf) is associated with frank malignancy (leiomyosarcoma). Ref: Robbin's Basics of Pathology , 7th Edition, Page I090; Oncology: An Evidence-Based Approach By Alfred E. Chang, 2006, Page 944.", 'role': 'assistant'}]