What is the FIGO (International Federation of Gynecology and Obstetrics) classification of myoma (uterine fibroids) in ultrasound?

FIGO Classification of Uterine Fibroids on Ultrasound

The FIGO (International Federation of Gynecology and Obstetrics) classification system categorizes uterine fibroids (leiomyomas) into nine types (0-8) based on their relationship to the endometrium and myometrium, which is essential for determining treatment approach and predicting outcomes. 1, 2

Classification System Overview

The FIGO system provides a standardized framework that replaces the traditional simple categorization of fibroids as submucosal, intramural, or subserosal. This detailed classification is critical because it directly impacts surgical planning, particularly for minimally invasive procedures. 1, 3

Submucosal Fibroids (Types 0-2)

• Type 0: Pedunculated intracavitary fibroid with no myometrial extension—entirely within the uterine cavity 1, 2
• Type 1: Submucosal fibroid with <50% intramural extension—majority projects into the cavity 1, 2
• Type 2: Submucosal fibroid with ≥50% intramural extension—majority within the myometrium but still distorts the endometrial cavity 1, 2

Intramural Fibroids (Types 3-5)

• Type 3: Contacts the endometrium with 100% intramural component—touches but does not distort the cavity 1, 2
• Type 4: Entirely intramural—no contact with endometrium or serosa 1, 2
• Type 5: Subserosal with ≥50% intramural extension—majority within myometrium but bulges toward serosa 1, 2

Subserosal and Other Fibroids (Types 6-8)

• Type 6: Subserosal with <50% intramural extension—majority projects beyond the serosa 1, 2
• Type 7: Pedunculated subserosal—attached to uterus by a stalk 1, 2
• Type 8: Other locations including cervical, parasitic, or broad ligament fibroids 1, 2

Imaging Approach on Ultrasound

Ultrasound is the first-line imaging modality for fibroid evaluation, though MRI provides superior characterization when fibroids are numerous or complex. 4, 2, 3

Key Ultrasound Features to Document

• Number and size of each fibroid (measure largest diameter in millimeters) 2, 5
• Precise location using FIGO classification type for each fibroid 5
• Relationship to endometrium: Determine if the fibroid distorts, contacts, or is separate from the endometrial cavity 1, 5
• Percentage of intramural extension for submucosal fibroids (critical for hysteroscopic resection planning) 1, 5
• Pedunculated nature and stalk width if present 1, 5

Advanced Ultrasound Techniques

• 3D transvaginal ultrasound improves visualization of the endometrial cavity relationship, with 87% sensitivity for submucosal fibroids compared to hysteroscopy 4
• Saline infusion sonohysterography (SIS) enables better delineation between endometrial pathology and submucosal fibroids, with excellent agreement (kappa 0.80) with hysteroscopy for classification 4
• 3D SIS accurately depicts the percentage of intracavitary component, which directly influences treatment decisions 4

Clinical Implications by FIGO Type

Types 0-2: Hysteroscopic Approach Candidates

Submucosal fibroids (Types 0,1, and possibly 2) are most commonly symptomatic and are best treated with transcervical resection of myoma (TCRM/hysteroscopic myomectomy). 1, 6

• Type 0 and 1 fibroids have the highest success rates with hysteroscopic resection 1
• Type 2 fibroids may require staged procedures or alternative approaches depending on the degree of myometrial extension 1
• These types are most frequently associated with heavy menstrual bleeding, infertility, and recurrent pregnancy loss 4, 1

Types 3-5: Laparoscopic or Open Myomectomy

• Intramural fibroids typically require laparoscopic or open surgical approach if symptomatic 6
• Type 3 fibroids may occasionally be accessible hysteroscopically if they significantly protrude into the cavity 1

Types 6-7: Minimally Invasive Options

• Subserosal fibroids are candidates for laparoscopic myomectomy, uterine artery embolization, or MR-guided focused ultrasound 4, 6
• These types less commonly cause menstrual symptoms but may produce bulk-related complaints 4

Critical Pitfalls to Avoid

• Do not rely on 2D ultrasound alone for submucosal fibroids when surgical planning is needed—3D ultrasound or SIS provides superior assessment of intracavitary extension 4
• Avoid misclassifying Type 3 fibroids as Type 2—the distinction between cavity distortion (Type 2) versus cavity contact without distortion (Type 3) fundamentally changes the surgical approach 1, 5
• Always assess for multiple fibroids—the presence of additional intramural or subserosal fibroids may alter the treatment plan even if a submucosal fibroid is the primary concern 2, 5
• Document the exact percentage of intramural extension for Types 1 and 2—this percentage determines feasibility of complete hysteroscopic resection 4, 1

Structured Reporting Template

A standardized ultrasound report should include 5:

• Total number of fibroids identified
• For each fibroid: FIGO classification type, three dimensions (length × width × height in mm), and specific anatomic location
• For submucosal fibroids: percentage of intracavitary versus intramural component
• Presence or absence of pedunculation and stalk characteristics
• Overall uterine dimensions
• Any associated findings (adenomyosis, endometrial pathology)