In non‐neoplastic esophageal tissues, the expression of hypoxia markers such as HIF‐1α, CA9, and GLUT1 is rare,20, 21, 22 but in ESCC, this expression increases as it invades deeper, and the high expression of hypoxia markers is associated with a poor prognosis.10, 12, 13, 14, 15, 16, 17. This evidence concerns the gene CA9 and esophageal squamous cell carcinoma.