Study of Expression of P16 in Premalignant and Malignant Lesions of Penis and Their Significance

Background & Objective: Penile squamous cell carcinoma (SCC) is an extremely rare malignancy. It is usually caused by chronic human papillomavirus (HPV) 16 and HPV 18 infections. This study was conducted to investigate the immunohistochemical overexpression of p16, a surrogate marker for HPV, and to evaluate its usefulness as a potential diagnostic biomarker. Methods: In this cross-sectional prospective and retrospective cohort study, 56 penile squamous cell carcinoma (SCC) specimens and five penile premalignant specimens were evaluated in Kasturba Medical College, Mangalore, India, from January 2013-December 2018 in terms of clinical and histopathological features. Immunohistochemical expression for p16 in cases and controls was evaluated. Statistical comparison of p16 expression among clinical features, histological subtype, grade, and stages of tumor were done. Results: Analysis of the pattern of p16 staining showed diffuse and strong nuclear and cytoplasmic expression in 32.8% of the cases. There was a highly significant association (P<0.001) of pattern of p16 expression among the HPV and non-HPV subtypes of penile carcinoma. p16 expression was not significantly associated with other prognostic parameters like site of the lesion, lymphovascular invasion, perineural invasion, histologic grade, and pathologic stage. Conclusion: Expression of p16 would be a useful tool in differentiation between the HPV-associated and non-HPV-associated subtypes of penile SCC that may be helpful in prediction of aggressiveness and invasive potential of the respective histologic subtypes.