Types of Fibroids and Where in the Uterus They Grow

Uterine fibroids are extremely common. The incidence rate is unknown and varies by study, but they can be detected in up to 80% of women by 50 years of age. Many people with fibroids don’t know they have them because many fibroids are asymptomatic. In other cases, fibroids can cause symptoms like heavy periods, pain, or trouble getting pregnant. 

The symptoms and severity can depend on what types of fibroids a person has, as well as their location and size. Symptoms overlap among the different types, but certain types can be more likely to cause certain symptoms. The most common symptom of all fibroids is heavy or prolonged menses.

Fibroids are all made up of muscle fiber that originates in the uterus. However, they are categorized by where they grow and the shape they take.

Here’s what you should know about the different types of fibroids. 

What Are Uterine Fibroids?

Uterine fibroids (also called uterine leiomyomas or myomas) are muscular tumors that grow in the uterine wall. These growths are quite common and are not considered cancerous. It's estimated that 80% of females will develop fibroids in their lifetime.

The cause of fibroids is unknown, however, being overweight or of African descent may be risk factors that influence a person's risk of developing them.

Pedunculated Fibroids

Pedunculated fibroids are fibroids that grow on a long stalk. These stalks can grow out of the uterine walls—both outside (subserosal) or inside (submucosal) the uterus.

No matter where they occur, pedunculated fibroids can be painful because the stalk that they grow on can twist, cutting off blood supply to the fibroid and causing shooting pain.

Subserosal Fibroids

Subserosal fibroids grow on the outside of the uterus. They are the most common type of fibroid.

Some subserosal fibroids grow directly on the uterus, while others are pedunculated subserosal fibroids on a stalk.

Since subserosal fibroids grow on the outside of the uterus, they don’t cause many issues with the reproductive system, such as heavy menstrual bleeding. However, they can cause other symptoms as they grow and compress the surrounding organs, like the bladder or bowel.

People with subserosal fibroids might:

• Feel bloated or have heaviness in their abdomen
• Have pelvic pain or lower back pain
• Become constipated or need to urinate frequently
• Experience painful sex

If you have a pedunculated subserosal fibroid, you might experience occasional sharp pain if the fibroid twists. 

Submucosal Fibroids

Submucosal fibroids are the most rare type of fibroids, and often the most problematic.

They grow underneath the lining of the uterus, called the endometrium. Since the endometrium is shed monthly during a person’s menstrual cycle, having fibroids here can cause complications with periods, including heavy bleeding and long periods. This heavy bleeding can lead to the development of anemia, which can cause fatigue, low energy, shortness of breath, and dizziness.

Submucosal fibroids can cause trouble with fertility. About 1% to 2% of infertility cases are attributed to fibroids, most often submucosal fibroids. These fibroids can distort the uterus and other reproductive organs such as the fallopian tubes, making it difficult for a person to get pregnant.

They can also grow on stalks, extending through the endometrium into the open space of the uterus. These fibroids can increase the risk of miscarriage or birth defects.

Intramural Fibroids

Intramural fibroids occur in the wall of the uterus, beneath the endometrium. These are a common type of fibroid.

Intramural fibroids are further classified by where they occur:

• An anterior intramural fibroid grows at the front of the uterus.
• A posterior intramural fibroid grows at the back of the uterus.
• A fundal intramural fibroid grows on the top wall of the uterus.

Intramural fibroids can cause symptoms that mimic those of subserosal or submucosal fibroids. They can affect the function of the uterus and the surrounding organs, depending on where they grow and put pressure.

Intramural fibroids can cause: 

• Pelvic pain
• Lower back pain
• Heavy periods
• Bleeding between periods
  
• Frequent urination
• Constipation

Treatments

The treatment for fibroids can be complex and highly individualized. Speak to your doctor about your goals for treatment, and whether you want to be able to get pregnant after treatment. Many treatments for fibroids are suitable only for people who do not want to become pregnant in the future. 

In some cases, you won’t need to treat your fibroids at all. Fibroids need to be treated only if they’re causing symptoms like heavy bleeding or trouble getting pregnant.

Hormonal Treatments

Hormonal birth control, like the pill, skin patch, vaginal ring, implant, shot, and hormonal IUDs, can help reduce menstrual symptoms like heavy bleeding, cramps, and pain.

Fibroid Removal

Surgery to remove fibroids (myomectomy) can help reduce bleeding and size-related symptoms. Whether or not a fibroid should be removed will depend on the types of symptoms it is causing. There is no clearly defined size that warrants fibroid removal, but if your fibroids are causing symptoms, speak with your doctor about the best course of treatment.

Hysterectomy

The only foolproof cure for fibroids is a hysterectomy, or surgery to remove the uterus. If you have lots of symptoms, including heavy menstrual bleeding, a hysterectomy is a permanent solution to your fibroids. However, you will not be able to get pregnant in the future if you have a hysterectomy. A hysterectomy is a major surgery associated with a six-week recovery period.

Embolization

Uterine fibroid embolization is a procedure to cut off blood flow to the fibroids. A very small catheter (tube) is inserted into a large blood vessel in the inner thigh and threaded up to an artery in the uterus. Tiny particles are then injected into the artery, which stops the flow of blood to the fibroid. This causes the fibroids to shrink over the span of weeks to months.

Myolysis

Myolysis, or focused ultrasound surgery, is a procedure that kills off the fibroid tissue using heat, cold, or high-frequency ultrasound. This can cause them to shrink. Pregnancy is not recommended following this procedure.

Medication

A new treatment called relugolix—an oral GnRH antagonist— is approved for use by the Food and Drug Administration (FDA) in combination with estrogen and progesterone for the treatment of heavy menstrual bleeding. This medication causes the ovaries to temporarily stop producing progesterone and estrogen, which can help stop heavy bleeding during menses.

Summary

Many people have more than one type of fibroid and the protocol for treating fibroids is highly individualized. The only cure for fibroids is a full hysterectomy. If you opt for a different procedure, you may need additional fibroid treatments in the future, since fibroids are likely to grow back. Your doctor will help walk you through the benefits and drawbacks of various types of treatment so that you can decide which is best.