Abstract 1123: Simultaneous p16/ki-67 expression in detection of high-grade squamous intraepithelial lesions, in women with ASC in cervical smears

Abstract Background Immunocytochemical staining for overexpression of the cell-cycle regulatory protein p16INK4a has been shown to be an efficient approach to triage to colposcopy women with cervical smears categorized as Atypical Squamous Cells (ASC). Overexpression of p16 is associated with the transforming activity of the HR-HPV-E7 oncoprotein in cervical dysplasia. Ki-67 is a marker of cell proliferation of dysplastic epithelium. The efficiency of p16 and Ki-67 separately has been widely described. In high-grade squamous intraepithelial lesion (H-SIL) and cancer they can be co-expressed and the identification of cells with double staining reactivity (p16/Ki-67) can be used as an indicator of H-SIL. We aim to evaluate the diagnostic performance of double p16/Ki-67 staining in the detection of underlying H-SIL in cytological smears of women referred to colposcopy due to an ASC cervical smear result. Design Prospective diagnostic test study. It took 18 months to complete the representative number of cases considering the prevalence of ASC in the colposcopy consultation. Samples were included from patients referred to colposcopy with a cytological diagnosis of ASC. Liquid based cytology was taken and processed to obtain a blank cytological preparation. The p16/Ki-67 staining was performed using CINtec Plus™. The immunoreactivity for both markers evidenced by one or more cervical epithelial cells with brown cytoplasmic immunostaining for p16, and nuclear red for Ki-67, was evaluated by two pathologists blind to colposcopy or biopsy results. Biopsies and/or endocervical curettage were obtained when the colposcopist considered necessary and they were considered as gold standard. In cases where there was no visible lesion and no biopsy was taken, colposcopy was considered gold standard and it was classified as: satisfactory/unsatisfactory, negative/normal or positive/abnormal. A high-grade biopsy lesion (≥ CIN2) with H&E was considered as a final diagnosis. Results There were 120 cases included of ASC (114 ASCUS and 6 ASC-H), from women between 18 and 82 years (mean=38.6). 90 (75.0%) cases had histological study: 62 (68.9%) biopsies and 28 (31.1%) endocervical curettages, of which 17 (14.28%) cases had ≥CIN2, and none were cases of invasive cancer. p16/Ki-67 staining was positive in 21 (17.5%) cases, (64.7% sensitivity for ≥CIN2). All the ASC-H cases (3, 100%), and 57.1% of ASCUS cases with ≥CIN2 as final diagnosis were positive to p16/Ki-67. The specificity of p16/Ki-67 dual staining was greater than 90%. Conclusions There was a p16/Ki-67 specificity that exceeded the values ​​published in other studies on this double staining, but, the positivity and sensitivity estimates were lower than reported previously. The variability of p16/Ki-67 staining in HSILs would reflect the heterogeneity of these lesions. Citation Format: Lia Barrios, Luis Alvis, Ines Benedetti. Simultaneous p16/ki-67 expression in detection of high-grade squamous intraepithelial lesions, in women with ASC in cervical smears [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1123.