Fibroid tumors are benign growths that appear on the muscular wall of the uterus. They are the most common tumors of the body. You may hear them called other names like leiomyoma, leiomyomata, or myoma. They range in size from microscopic to masses that fill the entire abdominal cavity. In some cases, fibroids can be as large as a full term pregnancy. Uterine fibroids can affect women of all ages, but are most common in women ages 40 to 50. In most cases, there is more than one fibroid in the uterus. Fibroids consist of dense, fibrous tissue and are nourished and sustained by the uterine arteries in almost every case.