What is Vaginal Cytology?
Vaginal cytology is a microscopic examination of cells collected from the vaginal cuff (the top of the vagina after hysterectomy) or vaginal walls, used primarily for surveillance in specific high-risk populations rather than routine screening. 1
Definition and Purpose
Vaginal cytology involves collecting cells from the vaginal surface using sampling instruments similar to those used for cervical cancer screening. 1 The test examines these cells microscopically to detect:
- Vaginal intraepithelial neoplasia (VAIN) - precancerous changes in vaginal tissue 2
- Vaginal cancer - though this is extremely rare (1-2 cases per 100,000 women per year) 1
- Recurrent disease in women with prior cervical or endometrial cancer 3, 4
When Vaginal Cytology is Indicated
Vaginal cytology should NOT be performed routinely in most women after hysterectomy. 1 The test is only appropriate in specific high-risk situations:
Women Who Should Receive Vaginal Cytology:
- History of cervical cancer - continue screening indefinitely while in reasonable health 1, 3
- History of CIN2/3 (high-grade cervical precancer) - continue for 20-25 years after treatment, even beyond age 65 3
- In utero DES (diethylstilbestrol) exposure - lifelong increased risk of vaginal cancer 1, 3
- Immunocompromised patients (HIV+, transplant recipients, chronic immunosuppression) 3
- Recent hysterectomy for CIN2/3 - every 4-6 months until three consecutive negative tests over 18-24 months 1
Women Who Should NOT Receive Vaginal Cytology:
Women who had hysterectomy for benign conditions (fibroids, bleeding, prolapse) should not undergo vaginal cytology screening. 1, 5 The evidence is clear:
- In 5,862 women screened after benign hysterectomy, the positive predictive value for vaginal cancer was 0% 1
- 663 vaginal cytology tests were needed to detect one case of dysplasia, with no cancers found 1
- No benefit in patient outcomes was demonstrated 1
Collection Technique
Vaginal cytology samples are obtained from the vaginal cuff (the closed top of the vagina after cervix removal), not from the vaginal walls or pool. 1 The sampling uses:
- Extended tip spatula or cervical broom to sample the vaginal cuff circumferentially 1
- Either conventional smear (cells placed on slide) or liquid-based cytology 1
- Timing is flexible with liquid-based cytology; conventional smears ideally collected 10-20 days after menses starts 1
Important Clinical Distinctions
Vaginal cytology is fundamentally different from cervical cytology (Pap test). 1 Key differences:
- Cervical cytology screens for cervical cancer in women with an intact cervix 1
- Vaginal cytology only evaluates the vaginal cuff after the cervix has been removed 1
- Vaginal cytology has much lower sensitivity and clinical utility than cervical cytology 5, 4
Test Performance Characteristics
The accuracy of vaginal cytology is limited:
- Sensitivity for detecting vaginal recurrence after endometrial cancer: 40% 4
- Specificity: 87.9% 4
- Positive predictive value: 7.3% (most abnormal results are false positives) 4
- Negative predictive value: 98.4% 4
Common Clinical Pitfalls
Never perform vaginal cytology without first confirming the indication through medical record review. 1, 3 Specific errors to avoid:
- Screening women after benign hysterectomy - this provides no benefit and leads to unnecessary interventions 1, 5
- Stopping surveillance too early in women with prior CIN2/3 - must continue for 20-25 years regardless of age 3
- Relying on patient verbal history alone - always verify hysterectomy indication through pathology reports 1, 3
- Performing colposcopy for atypical squamous cells of undetermined significance (ASC-US) or low-grade squamous intraepithelial lesion (LSIL) results - these do not require colposcopy 4
Management of Abnormal Results
When abnormal vaginal cytology is detected in appropriate surveillance populations, immediate colposcopy with directed biopsy is recommended. 2 The algorithm depends on findings: