What are fibroids?
Uterine fibroids are benign, hormone-dependent neoplasms (benign tumors) of the myometrium, which mainly consist of smooth muscle cells and are therefore classified as leiomyomas (from Greek leíos = “smooth” and mys = “muscle”). The leiomyoma is usually a nodular, encapsulated, round tumor. Fibroids can occur individually (solitary fibroids), but they are often distributed in large numbers in the uterus, which are then referred to as myomatosus uterus/fibroid uterus.
Fibroids were first described in 1973 by the British pathologist Matthew Bailey, and at the present time, uterine fibroids are one of the most common gynecological diseases.
Types of Fibroids
The size of a fibroid can vary, some grow up to 20 centimeters and in individual cases can grow to simulate a pregnancy in the 5th month.
The fibroids are mainly classified according to their location. There are three types of fibroids classified by their location:
- Intramural Fibroids: the most common are intramural fibroids. These grow in the uterine wall. If they are small, they do not change the shape of the uterus; if they increase in size, they may become ovoid-shaped.
- Subserosal Fibroids: the subserosal fibroids grow towards the serosa (outer margin of the uterus). When they increase in size, they can grow outward to such an extent that they are only connected to the uterus via a stalk and are then referred to as pedunculated myoma extending outside of the uterus.
- Submucosal Fibroids: Submucosal fibroids grow towards the internal uterine cavity. They are rare (5% of fibroids), but cause symptoms early on. Submucosal fibroids can also appear as pedunculated myomas and thus penetrate into the cervix uteri.
Causes and risk factors for the development of uterine fibroids
Although the exact cause is not yet fully understood, it has been established that both estrogen and progesterone play a key role in the development of fibroids. Some studies suggest that estrogen inhibits the tumor suppressor gene p53 in myoma tissue. This leads to an unchecked proliferation of the cells with an increase in the size of the myoma.
Presumably there is also a genetic predisposition for the development of uterine fibroids. It is believed that there are at least 145 different genes that influence the development of fibroids. Among other things, these genetic factors regulate the effect of hormones in the formation of myoma.
Some associated risk factors include:
- Early menarche – which refers to mensuration/menarche before 12 years of age. This is thought to be the result of increases the number of cell divisions, which increases the risk of mutations in the genes that control myometrium proliferation.
- Reproductive dysfunction (absence of childbirth) . Anovulation – with infertility allows for the continuous effect of estrogens on the myometrium which is unopposed. while pregnancy reduces the time of free exposure of estrogens to the myometrium as these hormonal effects are reduced during pregnancy.
- Obesity, leading to insulin resistance – increases the fraction of free estrogens. At the same time, the conversion of androgens to estrogens increases in adipose tissue – this mechanism is more important in postmenopausal women.
The growth of fibroids is multifactoral and along with hormonal factors which effect fibroid growth a certain role is played by hereditary predisposition. There is also an immune theory for the growth of fibroids: the rapid growth of fibroids is observed with pronounced immune disorders that contribute to increased cell growth, angiogenesis and inflammation. Various growth factors play an important role. Damage to the structure of the uterus: curettage, inflammation, mutations – lead to the expression of growth factors and increase the risk of uterine fibroids and endometrial pathology. Myoma of the uterus can proceed for a long time without pronounced clinical manifestations.
Myoma is one of the most common benign tumors in women. Postmortem, fibroids can be detected in 25% of women over the age of 30. The frequency peak is between the ages of 35 and 45.
The prevalence increases with age up to menopause. Fibroids are also known to be more common in African Americans and do not occur in postmenopausal women. In addition, fibroids are more common in nulliparous women (women who have never given birth) than in women with children.