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What Are Uterine Fibroid Cysts?

author image Robert Yazbek
A health writer, Robert Yazbek has a Bachelor of Science in microbiology from Florida Atlantic University and completed his post-baccalaureate education at Harvard University.
What Are Uterine Fibroid Cysts?
What Are Uterine Fibroid Cysts? Photo Credit Keith Brofsky/Photodisc/Getty Images

Uterine fibroids are non-cancerous tumors of the uterus. They are round solid masses most commonly located within the wall of the uterus, according to "Williams Obstetrics." They are composed of bundled uterine smooth muscle separated by fibrous connective tissue. Cysts are sacs containing fluid, semisolid or gas. Fibroids may become cysts when they overgrow their blood supply. This is called cystic degeneration.


Fibroids are present in 20 to 40 percent of women older than 35 years of age and are more prevalent in African American women than Caucasian, according to "NMS Obstetrics and Gynecology." Each tumor originates from one uterine muscle cell that multiplies and grows in response to the hormone estrogen. Uterine fibroids occur during the reproductive years. Fibroids are uncommon before the onset of puberty and regress after menopause. Why certain uterine muscle cells respond to estrogen and become fibroids is not understood. Alternative names for fibroid are leiomyoma, fibromyoma or myoma.

Signs and Symptoms

Most women with uterine fibroids have no symptoms. Symptoms depend on the number, size and location of the fibroids. During menstruation, one way the uterus stops bleeding is by contraction. When fibroids are present, they interfere with the contraction, sometimes resulting in heavy bleeding, which can cause iron deficiency anemia. When fibroids enlarge, they exert pressure within the pelvis and also the intestines, bladder and fallopian tubes. If fibroids protrude on the outside of the uterus or extend out from the uterus by a pedicle, they may exert pressure on the intestines and cause constipation. The very rare parasitic fibroids (attached to the colon) may cause bowel obstruction. If fibroids exert pressure on the bladder, the frequency of urination increases since bladder volume is reduced. If the fibroid becomes large, it may obstruct the urethra. Fibroids can distort the shape of the uterus, block fallopian tubes and prevent the fertilized egg from entering the uterine cavity, causing infertility. Fibroids near the cervix may cause pain with sexual intercourse and vaginal bleeding. Fibroids that extend into the uterine cavity (intracavitary) by a pedicle originating from the inner uterine wall cause bleeding between periods and cramping. Fibroids below the inner uterus lining (submucosal) may cause infertility by preventing the fertilized egg from implanting into the wall of the uterus, resulting in miscarriage.

Pregnancy Complications

Fibroids increase in size during pregnancy and may cause complications, depending on the number, size and location. Fibroids protruding into the uterine cavity may cause the fetus to lay sideways (transverse) instead of the normal head-first (cephalic) presentation, resulting in cesarean section instead of natural delivery. Large fibroids can occupy a portion of the uterine cavity and interfere with the growth and development of the fetus, resulting in premature labor.


Fibroids with no symptoms are usually incidental findings during an annual pelvic exam. They are confirmed by ultrasound and similar appearing anomalies (adenomyosis) are ruled out. Adenomyosis is the abnormal finding of the inner uterine tissue in the muscular layer of the uterus.


Fibroids that cause symptoms are removed. In the reproductive years, treatment is focused on removing the fibroids from the uterus and preserving fertility. The most common surgical procedure is a myomectomy and is performed by a laparoscope or hysteroscope, depending on the fibroid's location. Intracavity and submucosal fibroids are removed by hysteroscopic myomectomy. Fibroids on the outside the uterus are excised by laparoscopic myomectomy. Hysterectomy is a more aggressive treatment and may include removing--in addition to the uterus--the fallopian tubes and ovaries. The type of surgical procedure depends on the size of the fibroids, location, severity of symptoms and age of the patient.

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