SMAD4 and esophageal squamous cell carcinoma: Some of the above-described recurrent mutations in EAC were significantly less frequent in ESCC, including APC, ARID1A, CDH1, KRAS, PTEN and SMAD4, while mutations of other genes such as KMT2D, BAP1, CDKN2A and NOTCH1 were found less frequently in EAC.