Comparative Evaluation of Three Primary Antibody Clones for p16 Immunohistochemistry in Gynecologic Tumors

Background: p16 immunohistochemistry (IHC) serves as a surrogate marker for high-risk human papillomavirus (hrHPV) and is widely used in gynecologic pathology. However, few studies have directly compared the staining performance and reproducibility of different p16 antibody clones in this context. Methods: We retrospectively evaluated 176 gynecologic tumor specimens including 42 whole slide sections and 134 tissue microarray cores from the cervix, endometrium, vulva, and ovary using three fully automated p16 IHC assays: E6H4 (Ventana/Roche), JC8 (Agilent/Dako), and 6H12 (Leica). Two pathologists independently reviewed each case, and concordance and interobserver agreement were analyzed. Sensitivity, specificity, and Cohen’s κ statistics were calculated, with E6H4 serving as the reference. Results: All three antibody clones demonstrated excellent staining performance with preserved tissue morphology and minimal background artifacts. Concordance for p16 positivity/negativity was 100% across all clone pairings (95% CI: 97.9–100%). Interobserver reproducibility was also perfect, with a κ coefficient of 1.00 (95% CI: 0.94–1.00). Minor non-block staining patterns did not impair interpretability. Conclusions: Our findings indicate that E6H4, JC8, and 6H12 clones yield comparable staining results when used in conjunction with standardized automated protocols. These results support the practical interchangeability of these clones in clinical and research settings, particularly when cost, availability, or risk management require substitution. Laboratories should continue to perform internal validation and utilize external quality assurance programs when implementing p16 IHC.