AKR1C2 and esophageal squamous cell carcinoma: The expression of the top 20 up‐regulated genes was shown in Figure 1A, among which AKR1C2 was the prominent candidate gene of interest for the following reasons: first, it was significantly up‐regulated in the three pairs of RNA‐sequencing samples; second, its reported functions were controversial, even in the same kind of tumour; third, there were few studies about AKR1C2 in EC, including ESCC and oesophageal adenocarcinoma.