ACTA1 and esophageal squamous cell carcinoma: Images of the StO2, quantified using OXEI, and photomicrographs of immunohistochemical staining of HIF‐1α, CAIX, and GLUT1 and double immunohistochemical staining of CD31 and α‐SMA in a representative case of pT1b ESCC are shown in Figure 5B–F.