Peritoneal Cytology in Endometrial Cancer
Peritoneal washings should still be obtained and recorded during hysterectomy for endometrial cancer, but positive cytology no longer upstages disease or independently dictates adjuvant treatment decisions in the modern molecular era.
Current Staging Status
Since the 2009 FIGO revision, positive peritoneal cytology no longer increases disease stage 1. However, both FIGO and NCCN guidelines explicitly recommend that peritoneal washings continue to be obtained and results documented 1. The most recent 2025 ESGO-ESTRO-ESP guidelines have moved toward molecular classification-based risk stratification, with no mention of peritoneal cytology influencing treatment algorithms 2.
Clinical Significance Despite Staging Change
While removed from staging criteria, the evidence reveals important prognostic implications:
Positive cytology correlates with worse outcomes: In early-stage (IA-II) disease, positive cytology is associated with decreased 4-year overall survival (79.5% vs 92.2% for stage IA with negative cytology, HR 1.85, p<0.001) 3
Marker of occult disease: Patients with positive washings have significantly higher rates of lymph node metastasis across all histologic types (28.7% vs 6.9% for endometrioid adenocarcinoma, p<0.0001) 4. Among positive cytology cases, 64.3% had disease outside the uterus 5
Independent prognostic factor: Even after adjusting for other risk factors, positive cytology remains an independent predictor of both lymph node metastasis and decreased survival 3, 6, 4
Impact on Treatment Decisions
The key question is whether positive cytology should trigger adjuvant therapy:
Chemotherapy may improve outcomes: In patients with stage I-II disease and positive cytology, adjuvant chemotherapy was associated with increased survival (HR 0.62, p=0.03) 3
Current guidelines don't mandate treatment changes: The 2025 ESGO guidelines base adjuvant therapy decisions on molecular classification, stage, and traditional pathologic features (grade, myometrial invasion, LVSI)—not cytology status 2
Risk stratification context matters: For low-grade endometrioid tumors with positive cytology, the prognostic impact persists (HR 1.85, p<0.001) 3, suggesting these patients may benefit from treatment escalation despite otherwise favorable features
Practical Algorithm
When encountering positive peritoneal cytology:
Document but don't upstage - Record as additional pathologic finding, not stage modifier
Assess for occult extrauterine disease - Higher suspicion for lymph node involvement; ensure adequate lymph node assessment was performed
Consider in multidisciplinary discussion - Use as additional risk factor when deciding between treatment options within the same risk category (e.g., choosing external beam radiotherapy over vaginal brachytherapy for high-intermediate risk)
Lean toward chemotherapy inclusion - For patients where treatment intensity is borderline, positive cytology supports adding systemic therapy
Don't use as sole indication for treatment - Modern molecular classification should drive primary treatment decisions 2
Important Caveats
Surgical approach affects cytology rates: Minimally invasive surgery is associated with higher rates of positive cytology (4.4% vs 2.3%, OR 2.08) compared to laparotomy 7, possibly due to tumor manipulation or uterine perforation during morcellation. This technical artifact should be considered when interpreting results.
Contradictory evidence exists: One small study found no difference in outcomes between positive and negative cytology patients 8, but this is outweighed by multiple larger studies demonstrating prognostic significance 3, 6, 4, 5.
The molecular era changes everything: The 2025 guidelines emphasize that POLEmut, MMRd, NSMP, and p53abn classifications now drive treatment decisions 2. Positive cytology should be interpreted within this molecular context rather than as an isolated finding.