Types of Fibroids Explained
Fibroid Locations, Different Types, Sizes, & FIGO Classifications

- FIGO Fibroid Classification
- Fibroid Types: Pedunculated, Intramural, Submucosal, Subserosal, Other
- Fibroid Size Classifications Explained
- How Does Fibroid Size & Location Affect Symptoms?
- How Does Fibroid Size & Location Affect Pregnancy & Fertility?
- How Does Fibroid Size & Location Affect Treatment Options?

Fibroid Symptom Reliefin Los Angeles

Fibroid Classification
Fibroid classification can be done in different ways, but the most widely adopted classification system is the one set by the International Federation of Gynecology and Obstetrics (FIGO). FIGO fibroid classification is based on the fibroids location in the uterus. According to FIGO fibroid classification, there are 9 types of fibroids, which are assigned numbers ranging from 0 to 8 [1]. These numbers describe the location of the fibroid relative to the three main layers of the uterus: the inner lining of the uterine cavity called the endometrium, the smooth muscle of the uterine wall called the myometrium, and the outer surface of the uterus known as the serous membrane. Size and number of fibroids are not currently included in existing staging systems, which assess fibroids primarily on their location [2]. Under the FIGO fibroid classification system, you’ll see that uterine fibroids are described as either pedunculated, submucosal, intramural, or subserosal.

FIGO Fibroids Classification
Fibroid Type | Description |
Type 0 Fibroid | Pedunculated, intracavitary |
Type 1 Fibroid | Submucosal, <50% intramural |
Type 2 Fibroid | Submucosal, ≥50% intramural |
Type 3 Fibroid | Contact with endometrium, 100% intramural |
Type 4 Fibroid | Intramural |
Type 5 Fibroid | Subserosal, ≥50% intramural |
Type 6 Fibroid | Subserosal, <50% intramural |
Type 7 Fibroid | Subserosal, pedunculated |
Type 8 Fibroid | Other (e.g., cervical, parasitic) |
Uterine Fibroid Types
Pedunculated Fibroids
Pedunculated fibroids grow on small stalks on the inside of the uterus (intracavitary) or outside of the uterus (subserosal). Imagine one of the stalks twisting–pedunculated fibroids can cause intense episodes of acute pain! Type 0 fibroids and type 7 fibroids are considered predunculated fibroids.
Fibroid Type | Description |
Type 0 Fibroid | Pedunculated, intracavitary |
Type 7 Fibroid | Subserosal, pedunculated |
Intramural Fibroids
Intramural fibroids are located within the uterine wall. Some intramural fibroids can enlarge to span from the outer serosal surface, through the uterine wall, and all the way to the endometrium (the mucosal surface). These are known as transmural fibroids. While intramural fibroids don’t distort the uterine cavity, they are associated with reduced fertility outcomes, although not as significantly as submucosal fibroids [3]. In one study of 96 Italian women with fibroids, intramural fibroids were the most prevalent type identified on transvaginal ultrasound [4]. Type 3 fibroids and type 4 fibroids are considered intramural fibroids.
Fibroid Type | Description |
Type 3 Fibroid | Contact with endometrium, 100% intramural |
Type 4 Fibroid | Intramural |
Submucosal Fibroids
A submucosal fibroid is a type of intramural fibroid where part of the fibroid projects into the uterine cavity and another part resides in the smooth muscle of the myometrium. Because submucosal fibroids grow just underneath the uterine lining (the endometrium), they can reduce embryo implantation and pregnancy rates for couples using assisted reproductive technology to treat infertility. Women with submucosal fibroids may present with bleeding in between menstrual cycles. This is especially common with prolapsed submucosal fibroids [5]. In general, submucosal fibroids don’t seem to be as prevalent as subserosal or intramural fibroids [4]. Type 1 fibroids and type 2 fibroids are considered submucosal fibroids.
Fibroid Type | Description |
Type 1 Fibroid | Submucosal, <50% intramural |
Type 2 Fibroid | Submucosal, ≥50% intramural |
Subserosal Fibroids
Subserosal fibroids grow on the outside of the uterus. Because they aren’t located near the endometrium or uterine cavity, they have fewer reproductive consequences [3]. However, large subserosal fibroids can put pressure on the abdomen, bladder or rectum, causing symptoms like pain, a feeling of fullness or being pregnant, bloating, pelvic pressure, urinary urgency or constipation. Like intramural fibroids, subserosal fibroids are also quite common [4]. Type 5 fibroids and type 6 fibroids are considered subserosal fibroids.
Fibroid Type | Description |
Type 5 Fibroid | Subserosal, ≥50% intramural |
Type 6 Fibroid | Subserosal, <50% intramural |
Other Types of Fibroids
While most fibroids are benign, non-cancerous leiomyomas, some fibroids can be malignant. Leiomyosarcoma, a cancerous fibroid, is typically found in older, postmenopausal women who complain of new pain with or without bleeding in new or existing fibroids. Parasitic fibroids appear as abdominal masses but are found outside of and separate from the uterus. Cervical fibroids are found at the opening of the uterus and are rare. Type 8 fibroids are considered other types of fibroids (e.g., cervical, parasitic).
Fibroid Type | Description |
Type 8 Fibroid | Other (e.g., cervical, parasitic) |

Fibroid Sizes Explained
Fibroid Size Classification
Fibroid size classification is done to either estimate the fibroid volume, measure fibroid diameter on imaging studies, or to estimate the size of the enlarged uterus as a result of a growing fibroid. In one study, women with one or more fibroids had a median fibroid size of 5 cm3 by volume [4]. Small fibroids have diameters less than or equal to 20 mm and they enlarge the uterus to appear as it would at the 4th week of pregnancy. Average, medium-sized fibroids range between 20 and 60 mm in diameter and cause the uterus to appear as if it were at 10 or 11 weeks gestation. Large fibroids are greater than 60 mm in diameter and enlarge the uterus, making it comparable to a womb at 12 to 16 weeks gestation.
Fibroid Size and Type
Fibroid Size and Position
How Does Fibroid Size & Location Affect Symptoms?
How Does Fibroid Size & Location Affect Pregnancy & Fertility?

How Does Fibroid Size & Location Affect Treatment Options?
Medications
Uterine Fibroid Embolization
Myolysis
Endometrial Ablation
Myomectomy
Hysterectomy
Surgical vs. Non-Surgical Fibroid Treatments: Which Is Best?
When it comes to fibroid treatment, we believe that less is more. A less invasive procedure means less trauma, less risk, and shorter recovery time. Learn more about why we opt for UFE, the least invasive treatment for uterine fibroids.
Uterine Artery Embolization
Fibroid Specialist in Los Angeles
Learn more about Los Angeles Fibroid Specialist Dr. Michael Lalezarian.
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