The Four Types of Fibroids & Their Locations

Subserosal fibroids, located on the outer part of the uterus’s muscle layer, create a bulge on the uterine wall. Emerging from the cells beneath the outer layer, they are associated with the serosa, the uterus’s outermost layer. Being located on the outer layer of the uterus, subserosal fibroids can develop a stalk and become pedunculated masses. This positioning also increases the likelihood of pressing on adjacent structures like the bladder, bowel, or ureter. Consequently, common symptoms include heavy bleeding caused by increased blood flow to the uterus and compression symptoms from organ pressure.

Intramural fibroids are fibroids located wholly within the muscle layer of the uterus. These are the commonest fibroids and may be particularly small or can be large so that they may either become subserosal or submucosal where they enter the cavity of the uterus. It is possible with large intramural fibroids that they go all the way between the inside or submucosal part of the uterus and the subserosal surface. Symptoms are again either menorrhagia or heavy periods, compression symptoms with very large fibroids or abnormal uterine bleeding where bleeding occurs at unexpected times. Pain usually only occurs in pregnancy.

Submucosal fibroids are fibroids that enter wholly, or usually partially within the cavity of the uterus. These fibroids are usually relatively small being less than 4 cm. Symptoms are usually menorrhagia, heavy bleeding or irregular spotting because of their location. These fibroids can also develop on a stalk and mimic polyps or are noticed as fibroids on a stalk. It is possible for these fibroids to interfere with pregnancy by interfering with implantation in early pregnancy.

As mentioned previously, pedunculated fibroids or fibroids which are present on a stalk and are either subserosal, that is on the outside of the uterus and the stalk is attached to the uterine wall with a fibroid on the other end, or they may be submucosal fibroids within the cavity of the uterus, again attached by a stalk. The commonest symptoms again are heavy or abnormal uterine bleeding or less often compression by the subserosal variety.

Fibroids are common and are often totally asymptomatic. They may be found coincidentally on an ultrasound or an examination and if they are not producing any symptoms at all and are not large, they may often be left alone and just monitored, often with serial ultrasounds. If fibroids are located wholly within the cavity or largely within the cavity of the uterus, they may be removed by inserting a hysteroscope (telescope) under general anaesthetic and the fibroids can be dissected out using a special instrument. This is especially possible if the fibroids are small and are just causing abnormal uterine bleeding.

If the main symptom is heavy bleeding and the fibroids are not located within the cavity of the uterus, a Mirena or progesterone releasing IUD or a medication called tranexamic acid which reduces the extent of bleeding may be suitable conservative forms of treatment. Fibroids have also been treated by artery embolisation where small coils are placed by an interventional radiologist in through the groin and up into the nutrition supplying artery to the fibroid. Similarly, fibroids can be microwaved and again this has a variable success rate and only reduces the size of the fibroid. This reduces the size of the fibroid but does not totally remove the fibroid.

More definitive surgical treatment involves either myomectomy where the fibroid can be excised often as a keyhole procedure or in the case where the woman has completed her family and has significantly large fibroids, the uterus can be removed, that is a hysterectomy may be performed. This may be performed without the removal of the ovaries in women who are premenopausal.

Associate Professor Len Kliman has been assessing, diagnosing and treating fibroids for over 30 years. Part of the management of these women has been the general assessment of women presenting with heavy or abnormal uterine bleeding which needs careful consideration.