CDKN2A and cancer: Although a surrogate marker, the utilization of p16INK4a IHC staining as a defining criteria for HPV-associated OPSCC has been included in the 8th Edition of the AJCC cancer staging manual as well as the latest edition of the World Health Organization (WHO) reference text on Head and Neck Tumours and as such it is advisable to include assessment of p16INK4a IHC in any study involving OPSCC to enable cross-comparisons [9, 12].