CDKN2A and esophageal squamous cell carcinoma: Contrastingly, the nonstop mutations in the cancer gene CDKN2A (9) are found in different entities including lung squamous cell carcinoma (2), lung adenocarcinoma (2), lung small cell carcinoma (1), head and neck squamous cell carcinoma (1), esophagus squamous cell carcinoma (1), pancreas ductal adenocarcinoma (1) and malignant melanoma (1).