MKI67 and head and neck squamous cell carcinoma: Given the role of CDKN2A and Ki-67 proteins in important cellular processes, including the proliferation and regulation of the cell cycle, it was hypothesized that the levels of those proteins would be changed in the tumor samples as compared with the margin samples depending on selected demographic and clinical–pathological characteristics in our study group with head and neck squamous cell carcinoma (HNSCC).