To test this hypothesis, we examined the frequency of PD-L2 and PD-L1 positivity in 100 ESD cases with early-stage tumours because ESD is often performed for cases with superficial oesophageal cancer without metastasis in Japan.25,26 Out of 100 cases, 27 (27%) cases were PD-L2 positive and 18 (18%) cases were PD-L1 positive. This evidence concerns the gene PDCD1LG2 and carcinoma of esophagus.