Womens Health

Profile on Uterine Leiomyomata

Woman's Diagnostic Cyber Disease Profile

Name: fibroids of the uterus

Synonyms: uterine leiomyomata, leiomyoma, myomas, myoma

General description: These are benign muscle growths of smooth muscle cells along with fibrous tissue from the main body of the uterus. The muscle cells grow in whirls that form ball-shaped growths varying from 1 mm to over 20 cm in diameter. If the growth starts near the outside of the uterus, the growth becomes a subserosal fibroid. If it starts near the middle of the uterus it is an intramural fibroid. And if it starts near the inside endometrial lining, it becomes a submucosal fibroid and can cause abnormal bleeding problems.

Malignancy in a fibroid is called a leiomyosarcoma and while it can be as high as 1-2% unsuspected in series of surgery for fibroids (1), it is generally considered to be less than 0.5% of all fibroids because only the enlarged fibroids causing symptoms end up coming to surgical treatment.

Is it common?

Traditional text books give a 20-25% incidence of women having fibroids at some time during their life but most evidence indicates it is much higher. The incidence may depend upon the ethnic background of the population examined. A study of Scandinavian women undergoing transvaginal ultrasound had a smaller overall incidence at 5-10% with the higher numbers being in the older age groups (2). We know however, that there is a racial difference with black women having 3 times higher an annual incidence of developing fibroids (3% vs 1%) (3). One pathological study of hysterectomy specimens demonstrated that if the number of tissue sections was increased over the normal number that pathologists usually take, then the incidence of fibroids tripled (4). This means that many uteri have small fibroids that are not clinically evident so incidence figures are dependent upon the method used to detect them. One recent study using pelvic ultrasound in asymptomatic women in the U.S. aged 35-49 found that over 50% of women who did not have a previous diagnosis of fibroids did have fibroids on ultrasound exam (4a). This study estimated the cumulative incidence of fibroids by age 50 was over 80% in black women and over 70% in white women. Thus the answer is that fibroids are very common. They are slightly more common and occur earlier in black women. Differentiating
features These tumor growths are generally asymptomatic. Often, they are first felt on a pelvic exam. Fibroids usually present as a central lower abdominal mass rather than totally involving the adnexa. Ultrasound or magnetic resonance imaging often can differentiate uterine leiomyomata from ovarian tumors, but not always. Malignancies such as leiomyosarcoma, mixed mesodermal sarcoma or endometrial stromal sarcoma may appear on MRI as a degenerating fibroid and cannot as yet be differentiated from a benign fibroid undergoing degeneration (5).

Microscopic analysis is the gold standard to differentiate a benign leiomyoma from a malignant leiomyosarcoma. The pathologist looks for the active number of cell mitoses per high power microscopic field. The definition of less than 5 mitoses per 10 high powered fields (6) or less than 4 mitoses (7) is a commonly used criteria for declaring a fibroid as benign but the pathologist also looks for cellular atypia and coagulative tumor cell necrosis and sometimes DNA ploidy in making this judgement (8,).

Other features

Pelvic pressure and fullness presents when the size of the uterus with the fibroids(s) grows as big as a 3-4 month pregnancy. If the fibroids are on the anterior uterine surface they can cause bladder pressure and urgency and if on the posterior surface, they may produce rectal urgency.

Abnormal menstrual bleeding is a problem if there is one or more submucosal fibroids or if an intramural fibroid gets so big it impinges upon the endometrial cavity and compromises the blood supply to the base of the uterine lining.

Pain is not a common symptom of fibroids. Most of these tumors are asymptomatic except when they increase in size, the weight alone causes pelvic discomfort. Leiomyomata can produce acute pelvic pain if they outgrow their blood supply. This is called degeneration of a leiomyoma and the pain lasts for several days to a week or more. Degeneration of smooth muscle can be like a heart attack of the uterus. Monthly menstrual pain or cramps is not characteristic of myomas and should signal a search for coexisting adenomyosis.


Fibroids are composed of uterine smooth muscle cells that are "monoclonal", i.e., all of the muscle cells in a leiomyoma are descendents of one cell that has reproduced itself extensively (10). It is not known whether the initial or ongoing stimulus is genetic, viral, inflammatory repair of normal cell loss or any other cause.

Fibroids grow in size if estrogen and progesterone is present and do not increase in size if estrogen and progesterone levels are low (11). Birth control pills probably play a role in stimulating fibroid growth and the fibroids may regress in size when the pills are stopped (12). As to whether oral contraceptives cause an increased fibroid incidence, the studies are somewhat conflicting from no increased incidence to a slightly increased incidence.

It was previously thought that just estrogen was necessary for growth but it now appears the progesterone is critical to fibroid growth.

Unnecessary studies

Unless there is an extremely high suspicion of malignancy based upon size, contour and MRI characteristics, transcervical core needle biopsy is unnecessary prior to surgery because the incidence of malignancy is so low. Natural history
untreated Fibroids are almost unknown before an adolescent starts having menstrual periods. They grow slowly unless they are under the stimulation of extra estrogen and progesterone such as oral contraceptives. After menopause, the fibroids and entire uterus get smaller unless hormone replacement therapy is given

Taking postmenopausal estrogen and progestin replacement therapy can cause fibroids to grow. It appears that the progesterone/progestin component is needed because that is the hormone that increases cell reproduction (mitotic activity) in the fibroid itself.

Fibroids shrink as more time after menopause passes. They may become calcified and it is not unusual to have an incidental finding on xray or ultrasound in the decade of the 70's and 80's show round calcified areas in the region of the uterus.

Goals of therapy (Rx)

Prior to menopause the goal is to keep the fibroids from growing too large or too fast. If a woman can get to menopause without having symptoms from the fibroids, then it is likely that she will never have problems from the growths that require treatment. If there are symptoms of abnormal uterine bleeding, the therapeutic goal becomes to control the bleeding. If the symptoms are pelvic pressure due to size of the fibroids, surgical removal, myomectomy, hysterectomy, or medical shrinkage of the fibroids is the goal. 1st choice therapy Therapy is very dependent upon what symptoms a woman is having and whether she is trying to conceive now or in the not too distant future.

For fibroids suspected to be causing infertility, difficulty carrying a pregnancy, or interfering with labor and delivery of a pregnancy, surgical removal (myomectomy) either by laparoscopy or by laparotomy is the procedure of choice.

If abnormal bleeding is a major symptom and there is any suspicion from ultrasound or saline sonohysterography of an abnormal uterine cavity shape, hysteroscopy and D&C with intent to perform a resection of any polyps or submucosal fibroids is the preferred treatment.

For symptoms of pelvic pressure or pain due to size, abnormal uterine bleeding not due to submucosal fibroids but associated with intramural fibroids, or suspected degeneration of fibroids, the preferred treatment is surgical removal of the fibroids. Hysterectomy is the treatment of choice for this since myomectomy has a significant recurrence rate, but treatment can also be performed by myomectomy if a woman wants future pregnancies or just wants to avoid removal of the uterus.

Other therapies used

  • Medical therapy using LHRF - This is not a good long term treatment when used alone because of the negative effects of lowered estrogen over the long term. It can be given with added estrogen (add back) after the first 3 months. One study using the anti-estrogen effect of LHRF (Depo-Lupron®) and giving estriol (a weak estrogen) add back therapy, does not reverse the uterine muscle and fibroid shrinkage from the LHRF.  This also appears to be true of conjugated estrogens given orally in conjunction with LHRF. They do not stimulate fibroid growth.
  • Laparoscopic fibroid myolysis (coagulation) of fibroids - This is the same as laparoscopic removal of fibroids only an electrical current, a laser, or a freezing probe is used to coagulate the fibroids making them lose their blood supply and eventually dissolve and scar over. This may be combined with endometrial ablation if future pregnancy is not desired.
  • Uterine fibroid embolization procedure had been used as a non surgical treatment. It is not totally benign nor necessarily safer than one of the surgical treatments. It has a significant amount of pain associated with it but it does seem to be about 65-89% effective in reducing pain and some bleeding.

Treatments to avoid

Birth control pills, especially the higher dose pills, should be avoided. They play a role in stimulating fibroid growth and the fibroids regress in size when the pills are stopped.

Progesterone alone causes fibroid muscle cells to reproduce and grow. If you give progestin alone as add back therapy to women treated with LHRF, the fibroids will return to pretreatment size. This implies that progestin supplementation alone (Provera®, DepoProvera®) will cause fibroids to grow.

Myolysis should not be performed if a woman is not using other forms of contraception to avoid pregnancy. There is a significant danger of uterine rupture during the pregnancy.

Reason for Rx choices

Hysterectomy is the treatment of choice if childbearing is completed because over a third of women have recurrences of fibroids whether they are removed by myomectomy, laparoscopic myomectomy or hysteroscopic resection of submucous or intramural fibroids.

Uterine fibroid embolization using polyvinyl alcohol (PVA) foam particles has about a 14% incidence of also inducing premature ovarian failure, especially in women in their 40's.

Laparoscopic fibroid myolysis (coagulation) of fibroids has about a 10% incidence of requiring further surgery such as a hysterectomy. If a woman inadvertently gets pregnant after a myolysis, there is a danger of uterine rupture during the pregnancy.


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