Uterine leiomyomas, leiomyomata, myomas
Uterine fibroids, also known as leiomyomata or myomas, are benign (noncancerous) smooth muscle tumors that are commonly found in the uterine wall (Pic. 1). Although the majority of women develop myomas during their fertile period, medical treatment is required only in a minority of cases, when the myomas present with symptoms affecting the quality of life.
Uterine fibroids are the most common solid tumors of the female genital tract. They arise from undifferentiated (mesenchymal) cells in the uterine body and imitate the muscular and connective tissue of the uterine wall. Typically, fibroids appear as well-defined, solid masses with a whorled appearance (Pic. 2). Despite the fact that their cause is still unknown, there is considerable evidence that estrogens (the primary female sex hormones) and progestogene (sex hormone released in the second half of the menstrual cycle) promote their growth, as the fibroids rarely appear before menarche and regress after menopause.
Growth and location are the main factors that determine if a fibroid leads to symptoms and problems. A small lesion can be symptomatic if located within the uterine cavity while a large lesion on the outside of the uterus may go unnoticed. Fibroids may be single or multiple. Most fibroids start in the muscular wall of the uterus. With further growth, some lesions may develop towards the outside of the uterus or towards the internal cavity.
Different locations (Pic. 3) are classified as follows:
Secondary changes that may develop within fibroids are hemorrhage (bleeding into the tumour), necrosis (tissue death inside the tumour), calcification, and cystic changes (development of a hollow space inside the tumour). They tend to calcify after menopause. If the uterus contains too many to count, it is referred to as diffuse uterine leiomyomatosis.
As the fibroids are estrogen and progesterone dependent, they occur in a large portion of women during their fertile period, and currently, no effective method of prevention that would simultaneously preserve the woman’s fertility is currently known.
Fibroids are related to infertility. There is a general agreement that submucosal leiomyomas negatively affect fertility, when compared to women without fibroids. Submucosal fibroids have a statistically significant negative effect on clinical pregnancy rates as reported by a meta-analysis of 13 studies, the study also showed a lesser extent of intramural fibroids on clinical pregnancy rates. About delivery rates, submucosal and intramural fibroids showed a negative impact. On the contrary, subserosal myomas did not show any effect on clinical pregnancy rates and delivery rates. Thus, submucous and intramural LMs are more involved for sterility and infertility cases due to alteration of uterine cavity and contractility, while subserosal fibroids do not seem to generate any obvious fertility issue.
However, it is still not entirely clear how fibroids may cause infertility. The possible mechanism of impairing fertility also depends on the localization of the fibroid. As mentioned above, the type of fibroids most commonly associated with reduced fertility are submucosal fibroids. It is possible that these fibroids divert the blood flow from the overlying region of endometrium (uterine lining), which impairs its growth and proper function, and may prevent the embryo from successfully implanting.
A much more rare cause of reduced fertility are subserosal fibroids. Depending on their localization, large subserosal fibroids can obstruct the opening of the uterine tubes into the uterine cavity, preventing the embryo from entering the cavity and implanting. Very large or multiple fibroids that alter the overall shape of uterine cavity may be also associated with adverse pregnancy outcomes, such as miscarriage or abnormal fetal presentation, as the deformed uterus is not able to properly accomodate the developing fetus.
Most of the fibroids do not cause any symptoms and are well tolerated by the patients. During pregnancy, the fibroids may grow rapidly due to elevated estrogen and progesterone levels, but they usually tend to shrink back after childbirth. Depending on their size and localization, fibroids may interfere with fertility, usually by preventing the egg from entering uterine cavity or preventing the embryo from inplanting. In treatment of symptomatic fibroids, the specific method is decided on individual basis, mainly considering the severity of patient’s symptoms. Conservative approaches are preferred in fertile women due to possible risks of uterine surgery. For women after menopause, the definitive treatment of fibroids that continue to cause symptoms is hysterectomy.
Medical condition characterized by the presence of ectopic endometrial tissue within the myometrium.
The most common benign smooth muscle tumors of the uterus encountered in women of reproductive age.