Cervical Cancer Staging Using the FIGO System
Cervical cancer is staged using the International Federation of Gynecology and Obstetrics (FIGO) classification system, which is fundamentally based on clinical gynecological examination but was revised in 2018 to incorporate radiologic imaging and pathologic findings—particularly lymph node status—to improve staging accuracy from 79% to over 90%. 1, 2
Core Staging Methodology
The FIGO staging system relies on a hierarchical approach to assessment:
- Clinical examination remains the foundation, allowing worldwide standardization even in resource-limited settings 3, 2
- Imaging findings (designated "r") are now formally incorporated, with MRI preferred over CT for tumor extension assessment 3
- Pathological assessment (designated "p") takes precedence over radiological findings when both are available 1
- The method used to assign stage must be documented and reported 4
Essential Staging Workup
Clinical Assessment
- Gynecological examination to assess tumor size, vaginal extension, parametrial involvement, and potential bladder or rectal extension 2
Laboratory Tests
- Complete blood count including platelets 3, 2
- Renal function tests (critical, as hydronephrosis defines stage IIIB) 3, 2
- Liver function tests 3, 2
- Squamous cell carcinoma (SCC) antigen if squamous histology (useful for follow-up if initially elevated) 3, 2
Imaging Strategy
- MRI of pelvis and abdomen is the preferred modality with 90.9% precision for tumor extension assessment 3, 1, 2
- Imaging is mandatory for any clinically visible tumor or microscopic tumor with >5 mm invasion (stage IB or greater) 3, 2
- Chest CT for metastasis assessment 3, 2
- PET/CT shows high sensitivity for nodal disease and is increasingly important with the 2018 revision incorporating lymph node status 3, 2, 5
FIGO Stage Definitions
Stage 0
- Carcinoma in situ (preinvasive carcinoma) 1
Stage I: Tumor Confined to Cervix
Stage IA (Microinvasive): Invasive carcinoma diagnosed only by microscopy with stromal invasion ≤5.0 mm depth and ≤7.0 mm horizontal spread 1, 4
Stage IB: Clinically visible lesion confined to cervix or microscopic lesion greater than IA2 1, 4
Stage II: Tumor Invades Beyond Uterus
Stage IIA: Vaginal involvement (upper 2/3) without parametrial extension 1
Stage III: Extension to Pelvic Wall or Lower Vagina
- Stage IIIA: Lower third of vagina involved 1
- Stage IIIB: Pelvic wall extension and/or hydronephrosis or non-functioning kidney 1
- Stage IIIC (new in 2018): Lymph node involvement regardless of local tumor extent 1, 2, 4
Stage IV: Distant Spread
- Stage IVA: Bladder or rectal mucosa invasion, or extension beyond true pelvis 1
- Stage IVB: Distant metastasis (includes inguinal lymph nodes and intraperitoneal disease) 1
Critical Staging Principles
Important Caveats
- Extension to the uterine corpus is disregarded for staging purposes; only vaginal and parametrial extension determine stage 1
- Lymphovascular space invasion (LVSI) does not affect stage classification but is an important prognostic factor that must be documented 1, 2
- Bullous edema alone is insufficient to classify as Stage IV; actual mucosal invasion must be present 1
Clinical Impact of Accurate Staging
The distinction between stages has direct treatment implications:
- Tumors ≤4 cm without parametrial invasion (stages IA2-IIA1) are surgical candidates with radical hysterectomy and lymphadenectomy 2
- Tumors >4 cm or with parametrial/pelvic wall extension require primary chemoradiation 2
- The 4 cm threshold is critical because it determines whether surgery or chemoradiation is the primary treatment modality 3, 2
2018 Revision Rationale
The incorporation of imaging and lymph node status addresses the limitation that clinical staging alone had only 79% accuracy, whereas the revised system achieves over 90% precision 1, 5. This change reflects common clinical practice, differentiates prognostic outcomes more accurately, and guides treatment stratification more effectively 5.