Enzinger PC, Mayer RJ. Esophageal cancer. N Engl J Med. 2003;349:2241-52.
 Kato H, Fukuchi M, Miyazaki T, et al. Surgical treatment for esophageal cancer. Current issues. Dig Surg. 2007;24:88-95.
 Jung KW, Won YJ, Oh CM, et al. Prediction of Cancer Incidence and Mortality in Korea, 2017. Cancer Res Treat. 2017;49:306-12.
 Kelly RJ. The emerging role of immunotherapy for esophageal cancer. Curr Opin Gastroenterol. 2019.
 Rong L, Wang B, Guo L, et al. HER2 expression and relevant clinicopathological features in esophageal squamous cell carcinoma in a Chinese population. Diagn Pathol. 2020;15:27.
 Doi T, Piha-Paul SA, Jalal SI, et al. Safety and Antitumor Activity of the Anti-Programmed Death-1 Antibody Pembrolizumab in Patients With Advanced Esophageal Carcinoma. J Clin Oncol. 2018;36:61-7.
 Chen J, Jiang CC, Jin L, et al. Regulation of PD-L1: a novel role of pro-survival signalling in cancer. Ann Oncol. 2016;27:409-16.
 Integrated genomic characterization of oesophageal carcinoma. Nature. 2017;541:169-75.
 Black M, Barsoum IB, Truesdell P, et al. Activation of the PD-1/PD-L1 immune checkpoint confers tumor cell chemoresistance associated with increased metastasis. Oncotarget. 2016;7:10557-67.
 Chen N, Fang W, Zhan J, et al. Upregulation of PD-L1 by EGFR Activation Mediates the Immune Escape in EGFR-Driven NSCLC: Implication for Optional Immune Targeted Therapy for NSCLC Patients with EGFR Mutation. J Thorac Oncol. 2015;10:910-23.
 Kwon MJ, Rho YS, Nam ES, et al. Clinical implication of programmed cell death-1 ligand-1 expression in tonsillar squamous cell carcinoma in association with intratumoral heterogeneity, human papillomavirus, and epithelial-to-mesenchymal transition. Hum Pathol. 2018;80:28-39.
 Kwon MJ, Kim KC, Nam ES, et al. Programmed death ligand-1 and MET co-expression is a poor prognostic factor in gastric cancers after resection. Oncotarget. 2017;8:82399-414.
 Le DT, Durham JN, Smith KN, et al. Mismatch repair deficiency predicts response of solid tumors to PD-1 blockade. Science. 2017;357:409-13.
 Amin MB, American Joint Committee on Cancer., American Cancer Society. AJCC cancer staging manual. 8th ed. Chicago IL: American Joint Committee on Cancer, Springer; 2017. p. xvii, 1024 pages.
 Brown IS, Fujii S, Kawachi H, et al. Tumours of the oesophagus. In: R.D. O, Lam AK, Ochiai A, et al., editors. WHO Classification of Tumours Digestive System Tumours. 5th ed. Lyon, France: International Agency for Research on Cancer; 2019. p. 23-58.
 Kim R, Keam B, Kwon D, et al. Programmed death ligand-1 expression and its prognostic role in esophageal squamous cell carcinoma. World J Gastroenterol. 2016;22:8389-97.
 Hayashi M, Tamura G, Jin Z, et al. Microsatellite instability in esophageal squamous cell carcinoma is not associated with hMLH1 promoter hypermethylation. Pathol Int. 2003;53:270-6.
 Taieb J, Shi Q, Pederson L, et al. Prognosis of microsatellite instability and/or mismatch repair deficiency stage III colon cancer patients after disease recurrence following adjuvant treatment: results of an ACCENT pooled analysis of seven studies. Ann Oncol. 2019;30:1466-71.
 Lim SH, Hong M, Ahn S, et al. Changes in tumour expression of programmed death-ligand 1 after neoadjuvant concurrent chemoradiotherapy in patients with squamous oesophageal cancer. Eur J Cancer. 2016;52:1-9.
 Ito S, Okano S, Morita M, et al. Expression of PD-L1 and HLA Class I in Esophageal Squamous Cell Carcinoma: Prognostic Factors for Patient Outcome. Ann Surg Oncol. 2016;23:508-15.
 Tanaka K, Miyata H, Sugimura K, et al. Negative influence of programmed death-1-ligands on the survival of esophageal cancer patients treated with chemotherapy. Cancer Sci. 2016;107:726-33.
 Hatogai K, Kitano S, Fujii S, et al. Comprehensive immunohistochemical analysis of tumor microenvironment immune status in esophageal squamous cell carcinoma. Oncotarget. 2016;7:47252-64.
 Jesinghaus M, Steiger K, Slotta-Huspenina J, et al. Increased intraepithelial CD3+ T-lymphocytes and high PD-L1 expression on tumor cells are associated with a favorable prognosis in esophageal squamous cell carcinoma and allow prognostic immunogenic subgrouping. Oncotarget. 2017;8:46756-68.
 Chen K, Cheng G, Zhang F, et al. Prognostic significance of programmed death-1 and programmed death-ligand 1 expression in patients with esophageal squamous cell carcinoma. Oncotarget. 2016;7:30772-80.
 Jiang Y, Lo AWI, Wong A, et al. Prognostic significance of tumor-infiltrating immune cells and PD-L1 expression in esophageal squamous cell carcinoma. Oncotarget. 2017;8:30175-89.
 Balar AV, Galsky MD, Rosenberg JE, et al. Atezolizumab as first-line treatment in cisplatin-ineligible patients with locally advanced and metastatic urothelial carcinoma: a single-arm, multicentre, phase 2 trial. Lancet. 2017;389:67-76.
 Wakita A, Motoyama S, Nanjo H, et al. PD-L1 Expression Is a Prognostic Factor in Patients with Thoracic Esophageal Cancer Treated Without Adjuvant Chemotherapy. Anticancer Res. 2017;37:1433-41.
 Ng HY, Li J, Tao L, et al. Chemotherapeutic Treatments Increase PD-L1 Expression in Esophageal Squamous Cell Carcinoma through EGFR/ERK Activation. Transl Oncol. 2018;11:1323-33.
 Twyman-Saint Victor C, Rech AJ, Maity A, et al. Radiation and dual checkpoint blockade activate non-redundant immune mechanisms in cancer. Nature. 2015;520:373-7.
 Maeng CH, Lee J, van Hummelen P, et al. High-throughput genotyping in metastatic esophageal squamous cell carcinoma identifies phosphoinositide-3-kinase and BRAF mutations. PLoS One. 2012;7:e41655.
 Shigaki H, Baba Y, Watanabe M, et al. PIK3CA mutation is associated with a favorable prognosis among patients with curatively resected esophageal squamous cell carcinoma. Clin Cancer Res. 2013;19:2451-9.
 Mori R, Ishiguro H, Kimura M, et al. PIK3CA mutation status in Japanese esophageal squamous cell carcinoma. J Surg Res. 2008;145:320-6.
 Kim HS, Lee SE, Bae YS, et al. PIK3CA amplification is associated with poor prognosis among patients with curatively resected esophageal squamous cell carcinoma. Oncotarget. 2016;7:30691-701.
 Shigaki H, Baba Y, Watanabe M, et al. KRAS and BRAF mutations in 203 esophageal squamous cell carcinomas: pyrosequencing technology and literature review. Ann Surg Oncol. 2013;20 Suppl 3:S485-91.
 Matsumoto Y, Nagasaka T, Kambara T, et al. Microsatellite instability and clinicopathological features in esophageal squamous cell cancer. Oncol Rep. 2007;18:1123-7.
 Kagawa Y, Yoshida K, Hirai T, et al. Microsatellite instability in squamous cell carcinomas and dysplasias of the esophagus. Anticancer Res. 2000;20:213-7.
 Ludmir EB, Stephens SJ, Palta M, et al. Human papillomavirus tumor infection in esophageal squamous cell carcinoma. J Gastrointest Oncol. 2015;6:287-95.