Immunohistochemical p16 overexpression and Rb loss correlate with high‐risk human papillomavirus infection in endocervical adenocarcinomas

Aims: p16 is a sensitive surrogate marker for transcriptionally active high-risk human papillomavirus (HR-HPV) infection in endocervical adenocarcinoma (ECA); however, its specificity is not perfect.
Methods and results: We examined p16 and Rb expressions by immunohistochemistry (IHC) and the transcriptionally active HR-HPV infection by mRNA in-situ hybridisation (ISH) with histological review in 108 ECA cases. Thirteen adenocarcinomas of endometrial or equivocal origin (six endometrioid and seven serous carcinomas) were compared as the control group. HR-HPV was detected in 83 of 108 ECA cases (77%), including five HPV-associated adenocarcinomas in situ and 78 invasive HPV-associated adenocarcinomas. All 83 HPV-positive cases showed consistent morphology, p16 positivity and partial loss pattern of Rb. Among the 25 cases of HPV-independent adenocarcinoma, four (16%) were positive for p16, and of these four cases, three of 14 (21%) were gastric type adenocarcinomas and one of 10 (10%) was a clear cell type adenocarcinoma. All 25 HPV-independent adenocarcinomas showed preserved expression of Rb irrespective of the p16 status. Similarly, all 13 cases of the control group were negative for HR-HPV with preserved expression of Rb, even though six of 13 (46%) cases were positive for p16. Compared with p16 alone, the combination of p16 overexpression and Rb partial loss pattern showed equally excellent sensitivity (each 100%) and improved specificity (100 versus 73.6%) and positive predictive values (100 versus 89.2%) in the ECA and control groups. Furthermore, HR-HPV infection correlated with better prognosis among invasive ECAs.
Conclusions: The results suggest that the combined use of p16 and Rb IHC could be a reliable method to predict HR-HPV infection in primary ECAs and mimics. This finding may contribute to prognostic prediction and therapeutic strategy.