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 leiomyosarcoma, 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: Ans. is 'd' i.e., The number of mitoses per high power field The distinction of Leiomyosarcoma from Leiomyomas: It is based on the combination of: Degree of nuclear atypia Mitotic index Zonal Necrosis The most impoant single criteria is the number of nuclear mitoses present With or without Nuclear atypia (Independent of nuclear atypia) --> The presence of ten or more mitoses per ten high power (x400) fields indicates malignancy with or without cellular atypism. In presence of nuclear atypia or large cells --> 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'}]