In esophageal cancer cases, the frequency of mutations in NOTCH1, a cancer-associated gene, was significantly higher in the normal epithelium of the esophagus adjacent to the cancer than in the esophageal cancer (66% vs. 15%), and there were multiple mutations in NOTCH1 in the same clone of normal esophageal epithelium [24]. Here, NOTCH1 is linked to esophageal cancer.