[Evaluation of p16/Ki-67 double-stained immunohistochemistry in diagnosis of human papilloma virus-positive oropharyngeal squamous cell carcinoma]

Objective: To explore the diagnostic value of p16/Ki-67 double-stained immunohistochemistry in the diagnosis of human papilloma virus (HPV)-positive oropharyngeal squamous cell carcinoma(opscc) and find out the optimal index to improve the accuracy of HPV detection. Methods: A total of 153 cases, from May 2014 to May 2020, diagnosed OPSCC in Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, were selected. This cohort included 130 males and 23 females, aged (58.6±10.0) years old. HPV RNA in situ hybridization was chosen as the gold standard to detect their HPV status. p16 immunohistochemistry and p16/Ki-67 double-stained immunohistochemistry were performed on all cases, and the p16/Ki-67 double positive index including 20%, 40%, and 60% were used as the thresholds to compare their sensitivity, specificity, and positive prediction value (PPV), negative prediction value (NPV) and prognosis prediction ability. Results: Among the 153 patients with OPSCC, 114 were HPV-negative and 39 were HPV-positive, and the HPV infection rate of OPSCC patients was 25.5% (39/153). Only 58.1% (36/62) of single p16 positive cases were HPV-positive, and the prognosis of patients could not be distinguished using p16 immunohistochemistry only. Using p16/Ki-67 double staining, the accuracy of HPV positive diagnosis has been improved. The HPV diagnostic ability was the highest when the p16/Ki-67 double positive index was 40% (sensitivity=86.8%, specificity=94.8%, PPV=84.6%, NPV=95.6%, area under the curve=0.897), which could distinguish the prognosis of patients (P=0.012). Conclusions: The p16/Ki-67 double-stained immunohistochemistry can improve the accuracy of HPV positive diagnosis rate and diagnosis of HPV-positive oropharyngeal cancer is the most accurate when the double-positive index is 40% as the threshold to judge HPV status and could serve as better surrogate marker for HPV detection.