<prompt> With regard to the malignant behavior of leiomyosarcoma, the most impoant criterion isBlood vessel penetration by tumor cellsTumor cells in lymphatic channelsLymphocyte infiltrationThe number of mitoses per high power field  <response>: Option 4 is correctthe number of mitosis per high power field Leiomyosarcomas typically take the form of soft, hemorrhagic, necrotic masses. The diagnostic features of ove leiomyosarcoma include tumor necrosis, cytologic atypia, and mitotic activity. Robbins basic pathology 9th edition page no 694,headingleiomyosarcomas..boxMorphology ref img 