With regard to the malignant behavior of leimyosarcoma, the most impoant criterion is:
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.
Blood vessel penetration by tumor cells
Tumor cells in lymphatic channels
Lymphocyte infiltration
The number of mitoses per high power field