Fibroid Basics

Uterine fibroids, also known as leiomyomata or myomas, are benign (noncancerous) tumors of the muscular wall of the uterus. They are the most common tumor of the female genital tract and affect 1 in 3 women older than 35. Fibroids are classified based on their location within the uterine wall. Submucous (or submucosal) fibroids occur just under the endometrial lining of the uterine cavity. Intramural fibroids occur in the muscular wall. Subserosal fibroids occur under the outside covering of the uterus. As fibroids enlarge, the distinction between the types becomes blurred. Pedunculated fibroids occur on a stalk, project from the surface of the uterus, and can be confused with ovarian masses. They can project from the inner lining of the uterus and even extend through the cervix.

Each fibroid develops from a single cell, in the uterine wall, that undergoes transformation. The cause of this transformation is unknown but a genetic link has been established. The subsequent growth of the fibroid appears to be related to the female hormones estrogen and progesterone, as well as other growth factors.

Fibroids are common in all women but are particularly common in child bearing age African-American women where the incidence is up to 75%. They also tend to develop fibroids at an earlier age and to a greater extent. The incidence of fibroids is also increased in obese women. A lower incidence is noted in women who exercise and have lean bodies, smokers, those bearing more children, and those bearing children later in life.