Differential diagnosis of high-grade squamous intraepithelial lesions and benign atrophy in older women using p16 immunocytochemistry

Background: For cervical cancer screening, routine cytology has a high specificity but a lower sensitivity. In older women, atrophy, which may mimic HSIL, presents a diagnostic challenge. p16 is a widely used biomarker for histological diagnosis of HSIL. Our objective was to evaluate PathCIN® p16INK4a immunocytology in identification of high grade dysplasia vs. benign atrophy. Methods: As part of a multi-center screening program, 3351 women were co-tested by p16 immunocytology. Among women referred for colposcopy on basis of cytology and high-risk HPV status, those with atrophy were older than the population screened (52 vs. 43 years). Cases from older women with atrophy (n ​= ​116) and controls without atrophy (n ​= ​47) were identified by re-examination of Pap smears. The detection of CIN2+ was compared for p16, cytology and HR-HPV results. Results: The sensitivity of routine cytology (≥LSIL) was much lower for cases with atrophy (17%) than non-atrophic cases (75%). The sensitivity of p16 immunocytology and of HR-HPV testing was high (88%–100%) both with and without atrophy. The specificity of routine cytology (≥LSIL) was higher for cases with atrophy (79%) than non-atrophic cases (38%). The specificity of p16 immunocytology was high (88–95%) and the specificity of HR-HPV testing was low (31%–33%) both with and without atrophy. Combining p16 with HPV testing and/or routine cytology had no benefit, as compared to p16 staining alone. Conclusions: p16 immunocytology compares favorably with routine cytology and HPV testing in the differential diagnosis of HSIL and benign atrophy. It is more sensitive than cytology for atrophic specimens, and is more specific than HPV testing. p16 immunocytology may decrease the need for colposcopy referrals and could be a useful tool for early detection of cervical cancer in peri- and post-menopausal women, who are more likely to have HSIL coexisting with atrophy.