A fibroid is a noncancerous tumor composed of muscle and fibrous tissue.
Fibroids are also called fibromyomas, fibromas, myofibromas, leiomyomas, and myomas.
Fibroids in the uterus are the most common noncancerous tumor of the female reproductive tract. By age 45, about 70% of women develop a fibroid. Many fibroids are small and cause no symptoms. But about one fourth of white women and one half of black women have fibroids that cause symptoms. Fibroids are more common among women who are overweight.
What causes fibroids to grow in the uterus is unknown. High estrogen and progesterone levels seem to stimulate their growth. Thus, fibroids often grow larger during pregnancy and, to a lesser extent, before menopause, and they shrink after menopause. If fibroids grow too large, they may not be able to get enough blood. As a result, they begin to degenerate.
Fibroids may be microscopic or as large as a basketball. They may grow in different parts of the uterus, usually in the wall (which has three layers):
Some fibroids grow from a stalk (called pedunculated fibroids). Fibroids that grow in the wall or just under the endometrium can distort the shape of the interior of the uterus. Usually, more than one fibroid is present.
Symptoms depend on the number of fibroids present, their size, and their location in the uterus. Many fibroids, even large ones, do not cause symptoms. Fibroids, particularly those just under the lining, commonly make menstrual bleeding heavier or last longer than usual. Anemia may result from the loss of blood. Less often, fibroids cause bleeding between menstrual periods, after sexual intercourse, or after menopause.
Large fibroids, particularly those that grow in the wall of the uterus, may cause pain, pressure, or a feeling of heaviness in the pelvic area during or between menstrual periods. Fibroids may press on the bladder, making a woman need to urinate more frequently or more urgently. They may press on the rectum, causing discomfort and constipation. Large fibroids may cause the abdomen to enlarge. A fibroid growing from a stalk inside the uterus may twist and cause severe pain. Fibroids that are growing or degenerating usually cause pressure or pain. Pain due to degenerating fibroids can last as long as they continue to degenerate.
Fibroids that cause no symptoms before pregnancy may cause problems during pregnancy. Problems include miscarriage, early (preterm) labor, abnormal positioning (presentation) of the baby before delivery, and excessive blood loss after delivery (postpartum hemorrhage).
Rarely, fibroids cause infertility by blocking the fallopian tubes or by distorting the shape of the uterus, making attachment to the lining of the uterus (implantation) of a fertilized egg difficult or impossible.
Doctors can often detect fibroids during a pelvic examination. Doctors also use other procedures to examine the uterus and confirm the diagnosis:
Sometimes magnetic resonance imaging (MRI) is also done. Occasionally, additional tests are necessary.
If bleeding (other than menstrual) has occurred, doctors may want to exclude cancer of the uterus. So they may do a Papanicolaou (Pap) test, biopsy of the uterine lining (endometrial biopsy), ultrasonography, sonohysterography, or hysteroscopy. For hysteroscopy, a flexible viewing tube is inserted through the vagina and cervix into the uterus. A local, regional, or general anesthetic is used.
For most women who have fibroids but no bothersome symptoms or other problems, treatment is not required. They are reexamined every 6 to 12 months to determine whether fibroids are growing.
Several treatment options, including drugs and surgery, are available if bleeding or other symptoms worsen or if fibroids enlarge substantially.
A few drugs may be used to relieve symptoms or to shrink fibroids, but their effects are only temporary. No drug can permanently shrink a fibroid.
Synthetic forms of a hormone produced by the body called gonadotropin-releasing hormone (GnRH) are most commonly used. These drugs are called GnRH agonists (see Endometriosis: Drugs). Leuprolide and goserelin are most commonly used. They can shrink fibroids and reduce bleeding by causing the body to produce less estrogen (and progesterone). Because they shrink the fibroids and reduce bleeding, doctors may give GnRH agonists before surgery to make removal of fibroids easier, reduce blood loss, and thus reduce the risks of surgery. The drugs are injected once a month, used as a nasal spray, or implanted as a pellet under the skin. If taken for a long time, they may reduce bone density and increase the risk of osteoporosis. Estrogen may be given in low doses with GnRH agonists to help prevent these side effects.
Hormonal contraceptives, usually progestins (see Family Planning: Hormonal Methods), can control bleeding in some women. However, when women stop taking contraceptives, abnormal bleeding and pain tend to recur. Also, when some women are treated with contraceptives, the fibroids grow.
Raloxifene and related drugs (such as some selective estrogen receptor modulators, or SERMs) reverse some of estrogen's effects and can reduce fibroid growth.
Surgery is usually considered for women who have any of the following:
Surgery traditionally involves one of the following:
For hysterectomy, surgeons may use one of the following methods:
For myomectomy, surgeons may use laparotomy, laparoscopy (used to remove fibroids on the outer part of the uterus), or hysteroscopy. For hysteroscopy, they insert a telescope-like lighted device through the vagina into the uterus. This device can cut tissue and remove fibroids on the inside of the uterus. Which method is used depends on the size, number, and location of fibroids. Laparoscopy and hysteroscopy are outpatient procedures, and recovery is faster than recovery after an abdominal incision. However, laparoscopy often cannot be used to remove large fibroids, and the risk of complications after laparoscopy can be higher.
Other treatments can be used to destroy rather than remove fibroids.
For uterine artery embolization, doctors use an anesthetic to numb a small area of the thigh and make a small puncture hole or incision there. Then, they insert a thin, flexible tube (catheter) through the incision into the main artery of the thigh (femoral artery). The catheter is threaded to the arteries that supply blood to the fibroid, and small synthetic particles are injected. The particles travel to the small arteries supplying the fibroid and block them. As a result, the fibroid dies, then shrinks. Most of the rest of the uterus appears to be unaffected. However, whether the fibroid will regrow (because blocked arteries reopen or new arteries form) and whether the woman can become pregnant are unknown. The most common problems after this procedure are pain and infection.
Other procedures to destroy fibroids involve heat (high-intensity focused ultrasonography or radiofrequency ablation) or cold (cryoablation) via needle insertion, ultrasonography, or both. In myolysis, a needle that transmits an electrical current or heat is inserted into the fibroid and used to destroy the core of the fibroid. In cryomyolysis (a type of cryoablation), a similar procedure, a cold probe is used to destroy the fibroid. Whether women who have one of these procedures can become pregnant is unknown.
After these treatments, fibroids may grow back. In such cases, another treatment or a hysterectomy may be done.
Last full review/revision December 2008 by Bryan D. Cowan, MD