Intravenous leiomyomatosis of the uterus.

A case of intravenous leiomyomatosis of the uterus and 4 subperitoneal, pelvic leiomyomas without any connection to the uterus is demonstrated. The intravascular position of the tumors is proved by immunohistochemistry with positive reaction of antibodies against von Willebrand Factor. This rare growth pattern of benign leiomyoma of the uterus often shows extrauterine extension by intravascular growth within venous channels, sometimes causing cardiovascular complications. This tumor should not be confused with malignant neoplasia.