Regarding expression in ESCC, a systematic review and meta-analysis by Egebjerg et al. showed the estimated prevalence of HER2 positivity in ESCC to be 10% as assessed by in situ hybridization (ISH) and 8.6% as assessed by initial immunohistochemistry (IHC) followed by ISH, indicating potential for anti-HER2 targeted therapy in ESCC, for which there are studies underway [53]. This evidence concerns the gene ERBB2 and esophageal squamous cell carcinoma.