Demographic Profile of p16 Immunopositive and HPV DNA PCR Positive Oral Squamous Cell Carcinoma in a Large Cohort of Indian Patients.

Abstract

Background:The Indian subcontinent has the highest incidence of oral cavity squamous cell carcinoma in the world. The high incidence of tobacco chewing habit with or without smoking has been found to be the chief culprit. However in a minor subset of patients Human Papilloma Virus may play a role. Materials and Methods:A total of 800 cases of Oral squamous cell carcinoma were included in the study. The patients were given a questionnaire comprising of questions about demographic details and habits. The biopsy samples were routinely processed for immunohistochemistry for p16 (E6H4 clone, CINtec histology, Roche diagnostics). Cases with 2+/3+ positive nuclear staining with more than 75% cells immunopositive were taken as p16 immunopositive as per the AJCC criteria and were further subjected to HPV DNA PCR for which DNA was extracted from the formalin fixed paraffin embedded tissue. Results: Out of 800 OSCC cases 139 (17.37%) showed p16 immunopositivity by AJCC criteria. Out of these, 104 (104/139, 74.8%) cases were positive by HPV DNA PCR for HPV-16/18. Following patient characteristics were associated with a higher proportion of p16 and HPV DNA positivity–urban residence, vegetarian diet, illiteracy, graduate or higher education. No correlation was noted with gender, tobacco smoking or chewing habits, religion, occupation or site of tumor. The p16 immunopositivity was higher in the younger age group with no tobacco habits. Conclusion:A significant proportion of OSCC cases in India are associated with HPV infection. A higher percentage of p16 immunopositivity amongst younger patients with no tobacco habits points towards a distinct subset of patients in whom HPV may be the chief culprit and not just playing a supporting role.