This investigation was undertaken to estimate the clinical value of an immunohistochemical study of the expression of the biomarker p16ink4a in young and adolescent women showing ambiguous results (CINII) of a histological study of cervix uteri biopsy specimens. A prospective cohort study was conducted in 207 patients aged 18 to 25 years with CIN. The reproducibility (kappa coefficient) of the results of histological examination of cervix uteri biopsy specimens was estimated by two pathologists after conventional hematoxylin and eosin (HE) staining of the specimens and after additional p16ink4a expression estimation using an immunohistochemical assay (IHCA) in 75 patients with CINII. At the same time, the complete agreement coefficient was estimated to be 1 and the random agreement one was 0. The data were statistically processed using MedCalc 12.4.0.0. After examining the HE-stained specimens, the mean kappa value was 0.40, 0.34, 0.38, and 0.54; that in the micro slides treated by IHCA for р16ink4a expression was 0.45, 0.50, 0.72, and 0.75 for the unaltered samples from CINI, CINII, and CINIII areas, respectively. Furthermore, this coefficient increased from 0.54 (95% confidence interval (CI) 0.48-0.71) in the HE-stained specimens to 0.85 (95% CI 0.77-0.93) in the IHCA-treated micro slides for CINII + versus CINI cases. The indicator of p16ink4a expression in the cervix uteri biopsy specimens is a key criterion for choosing the management tactics in young and adolescent patients having ambiguous results of a histological study (CINII) of cervix uteri lesion. At this time, the probability of correcting the interpretation of biopsy results by one pathologist is substantially increased, which allows a reasoned excision or follow-up decision.