CDKN2A and cervical squamous intraepithelial neoplasia: Prime examples include Ki-67 (involved in cellular proliferation) and p16INK4a (a cell-cycle regulatory protein), both of which have been identified in prior studies as markers of CIN.4–8 Conversely, p16INK4a immunoreactivity is also observed in endocervical or metaplastic cells and in benign atrophic cells, requiring attention to cell morphology when interpreting stained specimens.9