Uterine Fibroids

What is a uterine fibroid?

Uterine fibroids are benign (non-cancerous) tumors that arises from the lining of the uterus. Other examples of benign tumors include skin moles, certain colon polyps, and skin tags. 

Approximately 33% of women develop uterine fibroids before the age of 50. 

Although fibroids are benign, they still cause a host of problems in some women. Fibroids can become extremely large and compress other structures within the abdomen and pelvis. Not uncommonly, uterine fibroids will grow to be larger than a grapefruit. 

The most common symptoms caused by uterine fibroids are:

  1. Heavy menstrual bleeding
  2. Severe menstrual cramping
  3. Frequent urination or inability to control urination
  4. Urinary retention caused by compression of kidneys 
  5. Pelvic pressure, discomfort, excessive bloating
  6. Abdominal wall distortion caused by large fibroids
  7. Pain with sexual intercourse

How are fibroids diagnosed?

Uterine fibroids are usually diagnosed during a routine gynecological examination. Doctors can frequently feel the enlarged fibroids during the physical exam. If a fibroid is felt, often an ultrasound will be ordered to confirm that the doctor is feeling a uterine fibroid as opposed to other types of gynecological masses.

Once you’ve been diagnosed with fibroids, your doctor will ask you questions to see if the fibroid(s) are causing problems like pain, bleeding, or abnormal menstruation. If you are not having problems, your doctor will see you in clinic for another physical exam in 6 months. If you are having problems then your doctor may order an MRI which gives excellent detail regarding the number and size of fibroids that are present. This information is very important if the fibroids need to be treated.

Types of uterine fibroids

There are three types of uterine fibroids which differ based on their location within the uterus. We will discuss the types of fibroids and the layers of the uterus together.

Endometrium (submucosal fibroids)

The first layer of the uterus is the endometrium which is the innermost layer of the uterus and is closest to the uterine canal. The endometrium is the layer of the uterus that grows every 4 weeks in preparation for pregnancy. If pregnancy doesn’t occur then the endometrium comes out of the woman’s vagina as her period. 

Fibroids that are located very close to the endometrium are termed submucosal fibroids. Submucosal fibroids are the rarest type of uterine fibroid and certain submucosal fibroids can distort the size of the uterine cavity and can sometimes block the fallopian tubes which can impair pregnancy.

Symptoms of submucosal fibroids include:

  1. Very heavy, excessive menstrual bleeding
  2. Prolonged menstruation
  3. Passing of blood clots during menstruation
  4. Anemia and or fatigue related to excessive bleeding

Myometrium (intramural fibroids)

The second layer of the uterus is the myometrium which is the middle layer. The myometrium is the muscular layer of the uterus and is the major layer responsible for muscle contractions.

Fibroids that develop within the myometrium are termed intramural fibroids which are the most common type of fibroid. When an intramural fibroid expands it distorts the uterine shape and causes the uterus to feel larger than normal. Intramural fibroids are heavily associated with “bulk symptoms” or symptoms related to the enlarged uterus pushing on adjacent structures.

Symptoms of myometrium fibroids, “bulk symptoms” include:

  1. Pelvic pain and pressure related to pressure on pelvic nerves
  2. Frequent urination or urinary urgency related to pressure on bladder
  3. Excessive bloating related to the fibroid uterus contacting the colon

Serosa (subserosal fibroids)

The third layer of the uterus is the serosa which is the outermost layer. This is a very thin layer that secretes a lubricating  substance to reduce friction between the uterus and nearby structures like the bladder and colon.

Fibroids that grow close to the serosa, i.e., near the outer lining of the uterus are termed subserosal fibroids. These fibroids are also referred to as pedunculated fibroids because they often grow on a stalk. Subserosal fibroids cause symptoms related to pressure on adjacent structures. Sometimes the stalk of a subserosal fibroid can twist and cause severe pain.

Symptoms of submucosal fibroids include:

  1. Heavy menstrual bleeding
  2. Menstrual periods lasting more than a week
  3. Pelvic pressure or pain
  4. Frequent urination
  5. Difficulty emptying the bladder
  6. Constipation
  7. Backache or leg pains

Can fibroids be cancerous?

Uterine fibroids are almost always benign (non-cancerous). It is important to note that doctors do not think that benign fibroids become cancerous, i.e., if a fibroid is benign then it is almost certainly always benign. In less than 1 in 1000 patients, a fibroid that is cancerous may look similar to a benign fibroid, i.e., the cancerous fibroid mimics a benign fibroid.

Having benign fibroids does not increase the risk of developing a cancerous fibroid, and benign fibroids do not increase the risk of getting other forms of cancer. It is usually easy for your doctor to determine if a fibroid is benign or cancerous based on your medical history and medical imaging (MRI). In some patients with abnormal symptoms or irregular imaging, your doctor may order an endometrial biopsy to confirm no evidence of cancer is present.

It should be mentioned that a certain surgical procedure termed morcellation, where a uterine fibroid  is broken into small pieces prior to removal, may be associated with the accidental spread of cancer if a fibroid happens to be cancerous. With uterine fibroid embolization, the fibroid is not cut or broken in any way; therefore, there is no association with spreading an unknown cancer. 

A graphic of a fibroid specialist and patient discussing fibroids treatment.

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