What is the FIGO (International Federation of Gynecology and Obstetrics) classification of Endometrial cancer?

FIGO Classification of Endometrial Cancer

The current FIGO staging system for endometrial cancer is the 2009 version, which is a surgical-pathological staging system that emphasizes myometrial invasion depth, cervical stromal involvement, and lymph node metastases, though a 2023 update incorporating molecular classification has recently been introduced. 1

Historical Context and Evolution

The FIGO staging system transitioned from clinical to surgical staging in 1988, requiring systematic pelvic and para-aortic lymphadenectomy for complete staging. 1 In May 2009, FIGO published a revised staging system that simplified several categories and better reflected the natural history of endometrial cancer. 1, 2 Most recently, a 2023 FIGO staging system has been introduced that incorporates molecular classification and tumor biology markers, representing a paradigm shift from purely anatomical staging to integrated risk-based staging. 3, 4, 5

FIGO 2009 Staging System (Currently Most Widely Used)

The 2009 FIGO staging system remains the foundation for most current clinical practice and research: 1

Stage I: Tumor Confined to the Corpus Uteri

• Stage IA: No myometrial invasion or invasion to less than half of the myometrium 1
• Stage IB: Invasion equal to or more than half of the myometrium 1

Stage II: Tumor Invades Cervical Stroma

• Tumor invades cervical stroma but does not extend beyond the uterus 1
• Key change from 1988: Stage II no longer subdivided into IIA and IIB; positive peritoneal cytology removed from staging 1

Stage III: Local and/or Regional Spread

• Stage IIIA: Tumor invades the serosa of the corpus uteri and/or adnexae 1
• Stage IIIB: Vaginal and/or parametrial involvement 1
• Stage IIIC: Metastasis to pelvic and/or para-aortic lymph nodes 1
  • Stage IIIC1: Positive pelvic lymph nodes 1
  • Stage IIIC2: Positive para-aortic lymph nodes with or without pelvic nodes 1

Stage IV: Tumor Invades Bladder/Bowel Mucosa and/or Distant Metastases

• Stage IVA: Tumor invasion of bladder and/or bowel mucosa 1
• Stage IVB: Distant metastases, including intra-abdominal metastases and/or inguinal lymph nodes 1

Key Differences Between 1988 and 2009 FIGO Staging

The 2009 revision made several critical changes: 1

• Stage I: Eliminated Stage IC designation; now only IA and IB based on 50% myometrial invasion threshold 1
• Stage II: Simplified to single category (cervical stromal invasion only); endocervical glandular involvement alone no longer constitutes Stage II 1
• Stage IIIA: Positive peritoneal cytology removed as staging criterion 1
• Stage IIIC: Subdivided into IIIC1 (pelvic nodes) and IIIC2 (para-aortic nodes) to better reflect prognosis 1

FIGO 2023 Staging System (Emerging Standard)

The 2023 FIGO staging represents a revolutionary approach by incorporating molecular classification and tumor biology: 3, 4, 5

• Molecular classification: Integrates four prognostic groups based on molecular testing: POLEmut (POLE mutated), MMRd (mismatch repair deficient), NSMP (no specific molecular profile), and p53abn (p53 abnormal) 3, 4
• Histopathological features: Incorporates histological type, grade for endometrioid tumors, and lymphovascular space invasion (LVSI) as integral staging components 3, 4
• Risk-based approach: Shifts from purely anatomical staging to risk stratification that better reflects biological behavior and prognosis 3, 5
• Most significant changes: Occur in Stages I and II, where sub-staging better reflects tumor biology 4

Clinical Implications and Staging Requirements

Preoperative Evaluation

• Chest X-ray, clinical and gynecological examination, transvaginal ultrasound, blood counts, liver and renal function profiles 1
• Abdominal CT scan for investigating extrapelvic disease 1
• Contrast-enhanced dynamic MRI: Best tool to assess cervical involvement when suspected 1
• FDG-PET/CT may be useful for detecting distant metastases 1

Surgical Staging Components

FIGO uses surgical and pathological staging requiring: 1

• Total hysterectomy with bilateral salpingo-oophorectomy 1
• Assessment of depth of myometrial invasion (ratio of invasion to total myometrial thickness) 1
• Peritoneal washings (though no longer affects staging in 2009 system) 1
• Systematic pelvic and para-aortic lymphadenectomy (debated; not shown to improve survival in randomized trials but provides prognostic information) 1
• Inspection and palpation of abdominal organs 1

Risk Stratification Based on Stage

Approximately 75% of patients present with Stage I disease, which can be subdivided into risk categories: 1

• Low risk: Stage IA, grade 1-2, endometrioid histology, no LVSI 1
• Intermediate risk: Stage IB, grade 1-2, endometrioid histology 1
• High risk: Stage IB grade 3, deep myometrial invasion with LVSI, or non-endometrioid histology 1

Important Clinical Caveats

Lymphadenectomy controversy: While systematic pelvic lymphadenectomy provides prognostic information and guides adjuvant therapy, randomized trials (Italian study, ASTEC trial) showed no improvement in disease-free or overall survival for routine lymphadenectomy in Stage I disease. 1 However, complete surgical staging is recommended for intermediate-high risk endometrioid cancer (Stage IA G3 and IB). 1

Sentinel lymph node mapping: An acceptable alternative to complete lymphadenectomy, with sensitivity of 97.2% and negative predictive value of 99.6% when using indocyanine green and following NCCN surgical algorithm. 1

Transition period: While the 2023 FIGO staging incorporates molecular classification, most existing literature and evidence base remains rooted in the 2009 classification, creating a transition period where both systems may be referenced. 1, 6