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 behaviour of leiomyosarcoma, the most important 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: The distinction of Leiomyosarcoma from Leiomyomas:\nIt is based on the combination of:\xa0\n\nThe degree of nuclear atypia\xa0\nMitotic index\xa0\nZonal Necrosis\n\nThe most important single criteria are the number of nuclear mitosis present\n\nWith or without Nuclear atypia (Independent of nuclear atypia) →\xa0The presence of ten or more mitoses per ten high power (x400) fields indicates malignancy with or without cellular atypism.\nIn presence of nuclear atypia or large cells\xa0→ If the tumor contains nuclear atypia or large epithelioid cells, five mitoses per ten high power fields are sufficient to justify a diagnosis of malignancy.', 'role': 'assistant'}]