CDKN2A and esophageal squamous cell carcinoma: This study is, according to our knowledge, the first study combining PCR, in situ hybridization, Ki-67 index, and p16INK4a immunohistochemistry, to investigate the role of HPV in ESCC carcinogenesis and the first study investigating HPV in ESCC in Malawi, a high-risk area for ESCC.