Anal intraepithelial neoplasia in women with genital intraepithelial neoplasia.

OBJECTIVE

To estimate the prevalence of anal intraepithelial neoplasia in heterosexual women with genital intraepithelial neoplasia, and to compare anal cytology with colposcopy for their effectiveness in anal intraepithelial neoplasia screening.

METHODS

Women with confirmed intraepithelial neoplasia on the cervix, vagina, or vulva were referred for gynecologic oncology care. All patients underwent anal cytology and high-resolution anoscopy. Any lesion detected on anoscopy was biopsied. Wilson score method was used to estimate 95% confidence interval for prevalence. McNemar's test compared the two screening methods.

RESULTS

Women with average age of 39.6 years (range 14 to 83 years) underwent anal cytology and anoscopy (N=205). Of the 205 patients with genital intraepithelial neoplasia, 25 patients (12.2%) had biopsy-proven anal intraepithelial neoplasia. Twelve patients (5.9%) had abnormal anal cytology (nine with atypical squamous cells of undetermined significance [ASC-US], three with low-grade squamous intraepithelial lesions [LSIL]). None of the nine patients with anal ASC-US had biopsy-proven anal intraepithelial neoplasia. Of the three patients with anal LSIL, two had anal intraepithelial neoplasia II and one had condyloma on biopsy. However, 78 patients (38%) had abnormal anoscopy findings that resulted in 25 biopsy-proven anal intraepithelial neoplasias (8 anal intraepithelial neoplasia I, 5 anal intraepithelial neoplasia II, 12 anal intraepithelial neoplasia III)), condylomas (n=11), and hyperkeratosis (n=8). Anoscopy identified 32% (25 patients) with anal intraepithelial neoplasia out of 78 abnormal anoscopic examinations. In diagnosing anal intraepithelial neoplasia, anoscopy has 100% sensitivity and 71% specificity; anal cytology has 8% sensitivity and 94% specificity.

CONCLUSION

Patients with cervical, vulvar, and vaginal intraepithelial neoplasia have 12.2% prevalence of anal intraepithelial neoplasia and should be screened with high-resolution anoscopy. In anal intraepithelial neoplasia screening, anoscopy is more sensitive but less specific than anal cytology.