They are most often found in the uterus but also in GI tract, blood vessels, etc. In the uterus, they are most commonly found in the myometrium of the corpus and rarely involve the uterine ligaments, the lower uterine segments, or the cervix. In the uterus, they can be intramural, subserosal, or submucous. In the uterus, they occur as a response to hyperestrinism. It is interesting to note that frequently leiomyomas will shrink, become fibrosed and calcified after menopause, and on the other hand can have a rapid increase in growth during pregnancy.
Leiomyomas are usually benign.
They may be asymptomatic or cause profuse bleeding at time of menstruation. They very rarely become malignant.