**2.1 Patient cohort**

Joint ethical approval for the research protocol was acquired from the Derbyshire Research Ethics Committee and Derbyshire Hospitals Research and Development office. Written, informed consent was obtained from all patients included in this study. EC samples and matched normal tissue taken from adjacent macroscopic mucosa from the same patient were collected from resected EC specimens of 34 patients [EAC: n = 28; ESCC: n= 6] who underwent esophagectomy. Normal samples were microscopically examined by a consultant pathologist to confirm normal features.
