RB1 and lip and oral cavity carcinoma: Immunohistochemical analysis has shown that the underexpressed RB protein in gastric adenocarcinoma [36] and low expression of p16 (encoded by CDKN2A) in oral carcinoma [31], vertical growth phase melanoma [32], esophageal squamous cell carcinoma [35], and GBM [38] significantly predict poor patient survival.