Prognostic role of immunohistochemical overexpression of the p16 protein in women under the age of 35 and diagnosed with HSIL (CIN2) subjected to “cervix sparing” excision

OBJECTIVE: To evaluate the role of immunohistochemical staining overexpression of p16 protein (p16 IHC) as a prognostic factor of persistence or recurrence of intraepithelial disease after excision procedure in young women diagnosed with HSIL (CIN2). PATIENTS AND METHODS: 62 women with a histological diagnosis of HSIL (CIN2) subjected to “cervix sparing” excisional procedure were included in this retrospective study. All had age less than or equal to 35 years, negative history of immunosuppression, available follow-up, and assessment of the resection margins state. Immunohistochemical staining for the p16 protein was evaluated on reviewed and confirmed HSIL (CIN2) histological specimens with negative resection margins. The post-treatment follow-up, including cytology, colposcopy, and histology, ranged from a minimum of 6 months to a maximum of 60 months. The persistence or recurrence of SIL during the follow-up period was based on histologic referral and defined as “the presence of SIL”, “the presence of HSIL” and “progression to HSIL (CIN3)”. RESULTS: 31/62 patients were positive for immunostaining (p16 IHC+), and 31/62 were negative (p16 IHC-). Persistence or recurrence after excision occurred more frequently within the p16 IHC+ than in p16 IHC- group, both as SIL (29% p16 IHC- vs. 32.3% p16 IHC+, p = 0.783) and HSIL (6.5% p16 IHC- vs. 12.9% p16 IHC+, p = 0.671). None of the patients in the p16 IHC-group showed progression to CIN3 for the entire observation period, whereas 9.7% of p16 IHC+ women progressed to CIN3 lesion (p = 0.042). The p16 IHC positivity showed a significant association with progression to CIN3 in 5 years of follow-up (p = 0.029) and with the presence of SIL after two years of follow-up (p = 0.031). The differences between the two groups increased after two years post-treatment: the p16 IHC- patients still had SIL only in 3.2% of cases and no longer had HSIL, while the p16 IHC+ women still showed SIL in 19.4% and HSIL in 6.5% of cases. The negative predictive value (NPV) of p16 IHC in predicting SIL’s presence after treatment increased with the severity of the lesion (NPV for SIL 70.97%, for HSIL 93.55%, for CIN3 100%). CONCLUSIONS: The study suggests that young patients with p16 IHC- HSIL (CIN2) have a better post-excisional course of the cervical intraepithelial disease compared to p16 IHC+ women and that p16 IHC could have prognostic utility during the long-term follow-up, especially in forecasting progression to CIN3 in consideration of the high NPV (up to 100%). The efficacy of the adjuvant HPV vaccination in the management of HSIL (CIN2) p16+ young women is to be evaluated as part of the fertility-sparing treatment.