What is the FIGO classification for uterine fibroids?

FIGO Classification for Uterine Fibroids

The FIGO classification system categorizes uterine fibroids into 8 types (0-7) based on their relationship to the endometrium, myometrium, and uterine serosa, providing a standardized framework essential for treatment planning and communication between clinicians 1, 2.

Classification System Structure

The FIGO system divides fibroids into three main anatomical categories with specific subtypes:

Submucosal Fibroids (Types 0-2)

• Type 0: Pedunculated intracavitary - entirely within the uterine cavity with no myometrial extension
• Type 1: Submucosal with <50% intramural extension - majority projects into the cavity
• Type 2: Submucosal with ≥50% intramural extension - majority within the myometrial wall

Intramural Fibroids (Types 3-5)

• Type 3: Contacts the endometrium with 100% intramural component - abuts the endometrial lining but doesn't distort the cavity
• Type 4: Entirely intramural - completely within the myometrium, no contact with endometrium or serosa
• Type 5: Subserosal with ≥50% intramural extension - majority within the wall but approaches the serosa

Subserosal Fibroids (Types 6-7)

• Type 6: Subserosal with <50% intramural extension - majority projects from the serosal surface
• Type 7: Pedunculated subserosal - attached to the uterus by a stalk

Additional Designation

• Type 8: Other locations - includes cervical, parasitic, or other atypical locations 3, 4

Clinical Significance for Treatment Planning

The FIGO classification directly determines treatment approach and predicts outcomes 5, 6:

Hysteroscopic Approach

• Types 0-2 are amenable to hysteroscopic myomectomy
• Type 0 and 1 have the best outcomes with hysteroscopic resection
• Type 2 may require two-stage procedures depending on intramural extension 7

Uterine Artery Embolization (UAE)

• Types 2-6 respond well to UAE
• Types 2/3 show superior outcomes: 54.7% volume reduction vs 39.8% for Types 4-7, with greater improvement in menstrual flow 8
• Type 7 (pedunculated) may be treated with UAE depending on stalk caliber, though surgical approaches are often preferred
• Cervical fibroids (Type 8) have less durable response to embolization 6

Surgical Planning

• Types 3-7 typically require laparoscopic or open myomectomy
• Critical pitfall: Types 2 and 3 that contact the endometrium may be expelled following UAE in 2.2%-7.7% of cases - patients must be counseled about this possibility 6

Imaging Recommendations

Ultrasound should be first-line for diagnosis, with MRI reserved for complex cases and surgical planning 1:

• Transvaginal ultrasound: 90-99% sensitivity for detecting fibroids, 90% sensitivity and 98% specificity for submucosal fibroids 6
• MRI: Superior for mapping multiple fibroids, changes management in up to 28% of cases, essential for accurate FIGO classification when planning minimally invasive procedures 6, 9

Reporting Standards

All imaging reports should use FIGO classification terminology to ensure standardized communication 1, 2. This includes documenting:

• Specific FIGO type for each fibroid
• Size and volume measurements
• Number of fibroids
• Relationship to endometrium and serosa
• Vascularity on Doppler imaging

The classification system has become the standard for clinical decision-making, particularly as minimally invasive techniques have evolved, requiring precise anatomical localization rather than simple descriptors like "submucosal" or "intramural" 9, 4.