A uterine fibroid (also uterine leiomyoma, myoma, fibromyoma, leiofibromyoma, fibroleiomyoma, and fibroma) is a benign (non-cancerous) tumor that originates from the smooth muscle layer (myometrium) and the accompanying connective tissue of the uterus.
Fibroids are the most common benign tumors in females and typically found during the middle and later reproductive years. While most fibroids are asymptomatic, they can grow and cause heavy and painful menstruation, painful sexual intercourse, and urinary frequency and urgency.
Uterine fibroids is the major indication for hysterectomy in the US. Fibroids are often multiple and if the uterus contains too many leiomyomatas to count, it is referred to as uterine leiomyomatosis. The malignant version of a fibroid is uncommon and termed a leiomyosarcoma.
About 20–40% of women will be diagnosed with leiomyoma. Estrogen receptors on fibroids cause them to respond to estrogen stimulation during the reproductive years. During hypoestrogenic states, such as after menopause, leiomyoma are expected to shrink. Leiomyoma are more common in overweight women (because of increased estrogen from adipose aromatase activity).
Uterine fibroids appear as round, well circumscribed (but not encapsulated), solid nodules that are white or tan, and show whorled appearance on histological section.
The size varies, from microscopic to lesions of considerable size. Typically lesions the size of a grapefruit or bigger are felt by the patient herself through the abdominal wall.
Microscopically, tumor cells resemble normal cells (elongated, spindle-shaped, with a cigar-shaped nucleus) and form bundles with different directions (whorled).
These cells are uniform in size and shape, with scarce mitoses. There are three benign variants: bizarre (atypical); cellular; and mitotically active.
For decades, Estrogen has been known to stimulate fibroids, but more recent studies have also revealed a possible role of progesterone and progestins to fibroid growth as well, and applicability of progestin agonists as part of treatment are currently being considered.
In very rare cases, malignant (cancerous) growths, leiomyosarcoma, of the myometrium can develop.
Fibroids that lead to heavy vaginal bleeding lead to anemia and iron deficiency. Due to pressure effects gastrointestinal problems are possible such as constipation and bloatedness. Compression of the ureter may lead to hydronephrosis. Fibroids may also present alongside endometriosis, which itself may cause infertility.Adenomyosis may be mistaken for or coexist with fibroids.
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Last Updated: Oct 14, 2014