P16 expression in subsets of Head and Neck squamous Cell Carcinoma in Kenyatta National Hospital

Abstract

Background: Traditionally head and neck squamous cell carcinoma (HNSCC) has been regarded as a homogenous group of tumours that differ only by anatomic site. However, numerous studies have indicated that this is not the case. Recognition of distinct molecular profiles now allows further classification of HNSCC into distinct subgroups that differ with respect to risk factors, pathogenesis, and clinical behavior. Among these subgroups is the Human papilloma virus (HPV) associated HNSCC which have been found to differ from the non HPV-associated HNSCC in that HPV-HNSCC affects younger patients, respond better to chemotherapy and radiotherapy and have a better 5 year survival rate independent of tumour stage. These subgroups cannot be readily differentiated morphologically on routine Hematoxylin and Eosin (H/E).Cellular tumour markers such as P16 Immunohistochemistry may be used to separate these groups of tumours. This study set out to identify the HPV associated HNSCC by P16 immunohistochemistry. This is due to the over expression of P16 tumour suppressor protein P16INK4A in these tumours. Several studies have found P16 immunohistochemistry has high sensitivity, specificity, positive and negative predictive value of P16 expression in relation to HPV status. P16 immunohistochemistry has been found to be a more cost effective method and it has been proposed to be used as a 1st line marker Objective: To determine P16 expression and the prevalence of HPV- associated tumours in subsets of Head and Neck Squamous cell carcinoma (Oral, Oropharyngeal, Laryngeal carcinomas) reported at KNH. Design: Laboratory-based, descriptive cross sectional study. Setting: The University of Nairobi (UON), Department of Human Pathology, and the Kenyatta National Hospital (KNH) Nairobi, Kenya Study population: A hundred and three cases reported as HNSCC (Oral, Oropharyngeal, Laryngeal carcinomas) Methods: A hundred and three previously diagnosed HNSCC from 2008-2013 were analyzed for P16 expression by Immunohistochemistry on formalin fixed paraffin wax embedded tumor tissue blocks. P16 expression was correlated with age, sex, anatomic site of tumor and histological differentiation.