It was reported that the intravascular tumor cells always exhibited ER and PR positivity, while the endothelial and subendothelial cells expressed none or scant or weak positivity; thus, it is likely that IVL originates from uterine leiomyomas.[6] IVL is more common in premenopausal women. This evidence concerns the gene ESR1 and Uterine leiomyoma.