An Emerging Anti-p16 Antibody-BC42 Clone as an Alternative to the Current E6H4 for Use in the Female Genital Tract Pathological Diagnosis: Our Experience and a Review on p16ink4a Functional Significance, Role in Daily-Practice Diagnosis, Prognostic Potential, and Technical Pitfalls

Background: To date, useful diagnostic applications of p16 IHC have been documented in gynecological pathology both for HPV-related and non-HPV-related lesions. In the present article, we reported our experience with the novel anti-p16 INK4a antibody (clone BC42), whose expression was tested across all different gynecologic neoplasms; we also compared it to the traditional E6H4 clone. Moreover, we discussed and explored all the diagnostic applications of p16 IHC in gynecologic pathology. Methods: Consultation cases covering a 5-year period (2016-2020) regarding gynecological neoplastic and non-neoplastic lesions in which immunohistochemistry for p16, clone E6H4 was originally performed, were retrospectively retrieved from the files of our institution. Immunohistochemical staining for p16ink4a (BC42) [Biocare Medical group-Paceco USA; Bioptica Milan] and p16ink4a (E6H4) [Ventana Medical Systems-Arizona USA; Roche] was performed by using the Ventana automated immunostainer (Ventana Medical Systems, Tucson, AZ, USA). The immunostaining pattern was defined as negative, focal/patchy, or diffuse. Results: A total of 196 cases, represented by 36 high-grade SIL/CIN3 of the uterine cervix, 30 cervical adenocarcinomas, 22 cervical squamous cell carcinoma, 70 endometrial carcinomas, 25 high grade serous ovarian carcinomas, 6 uterine adenomatoid tumors, and 10 uterine leiomyosarcomas were included in this study. Results showed concordant staining quality of both clones on all tested neoplastic tissues. Conclusions: The novel anti-p16 antibody (BC42 clone) appeared as an alternative to the current E6H4 for use in gynecological neoplasms, offering similar levels of positivity and equally reliable staining results.