NOTCH1 and esophageal squamous cell carcinoma: Despite possessing a mutational pattern characteristic of a tumor suppressor gene in head and neck, lung, skin, and esophageal SCCs and evidence demonstrating pro-oncogenic function in early oral tumorigenesis, NOTCH1 mutations occur significantly more frequently in normal esophageal epithelium (30–80%) than in ESCC (~10%) [120,123,124].