With regard to the malignant behavior of leiomyosarcoma, the most impoant criterion is ?

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.