CDKN2A and squamous cell carcinoma: For the verification of neoplastic processes (squamous cell carcinomas, adenocarcinomas), as well as for the differential diagnosis of various stages of HPV-associated carcinomas and metaplastic processes, Ki-67, Cyclin D1, and p16INK4a are most often used, being associated with the expression of HPV E7 during infection with oncogenic types of the virus, and with the anti-apoptotic p53 gene product.