Significance and limitations of routine p16/Ki-67 immunohistochemistry as a diagnostic tool for high-grade squamous intraepithelial lesions of the uterine cervix

Abstract

Objective To evaluate the diagnostic utility and limitations of routine p16 and Ki-67 immunohistochemistry (IHC) in detecting high-grade squamous intraepithelial lesions (HSILs) in the uterine cervix. Methods We reviewed 2, 061 cervical biopsy records, including 271 morphologically indeterminate squamous lesions, evaluated using p16/Ki-67 IHC for HSIL detection or exclusion. HSIL was diagnosed based on p16 positivity and a high Ki-67 labeling index (Ki-LI). In cases that remained inconclusive after IHC, follow-up histological and/or cytological outcomes were assessed. Results p16/Ki-67 IHC established a definitive diagnosis of either HSIL or non-HSIL in 74.2% (201/271) of morphologically indeterminate cases, whereas 25.8% (70/271) remained inconclusive. p16/Ki-67 IHC contributed to diagnosing 120 HSIL cases, representing 11.9% (120/1, 011) of all HSILs cases and 44.3% (120/271) of morphologically indeterminate cases. Among the 70 inconclusive cases, 58 had available follow-up data, of which 22 were subsequently diagnosed with HSIL, including 12 within 1 month of the initial biopsy. HSIL outcomes were more frequent in cases with suspicious HSIL on the initial biopsy (66.7% [12/18]). Based on the p16/Ki-LI status observed in the initial biopsy, patients with HSIL outcomes were categorized into three groups: p16-positive/low Ki-LI (54.2% [13/24]), p16-negative/high Ki-LI (50.0% [5/10]), and p16-negative/low Ki-LI (16.7% [4/24]). Multiple comparisons revealed a significant difference between the p16-positive/low Ki-LI and p16-negative/low Ki-LI groups (Benjamini-Yekutieli adjusted P=0.0435), while other comparisons were not significant. Conclusion p16/Ki-67 IHC significantly improved the diagnostic performance for HSIL. In cases that remain inconclusive after IHC, IHC-based risk stratification offers a valuable approach for surveillance, thus mitigating delays in HSIL diagnosis.