A uterine fibroid is a leiomyoma (benign (non-cancerous) tumor from smooth muscle tissue) that originates from the smooth muscle layer (myometrium) of the uterus. Fibroids are often multiple and garner the designation of diffuse uterine leiomyomatosis if they are randomly located and many in numbers. There is a malignant form of a fibroid and fibroids can rarely (0.1-0.5%), undergo malignant degeneration into leiomyosarcoma. Additionally there are rare forms of fibroids where the lesions are capable of metastasising without malignant transformation and this process is called benign metastasising leiomyoma.
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. Some fibroids may interfere with pregnancy although this appears to be very rare.
Fibroids, particularly when small, may be entirely asymptomatic. Symptoms depend on the location of the lesion and its size. Important symptoms include abnormal gynecologic hemorrhage, heavy or painful periods, abdominal discomfort or bloating, painful defecation, back ache, urinary frequency or retention, and in some cases, infertility. There may also be pain during intercourse, depending on the location of the fibroid. During pregnancy they may also be the cause of miscarriage, bleeding, premature labor, or interference with the position of the foetus. While fibroids are common, they are not a typical cause for infertility accounting for about 3% of reasons why a woman may not have a child. Typically in such cases a fibroid is located in a submucosal position and it is thought that this location may interfere with the function of the lining and the ability of the embryo to implant. Also larger fibroids may distort or block the fall