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were used as a marker of micrometastasis of squa-mous cell carcinoma. Thus, CTCs counts, as micrometastasis, might be related with SCC level.This study has some limitations. First, only a small number of patients were enrolled this study. Second, this study utilized a retrospective design. Recently, the sensitivity of CTCs detection reported to improve in other cancers17, 18), therefore, we would consider large sample sizes to the analysis in future. In conclusion, our results suggest that CTCs in preoperative peripheral blood has possibility to prognostic marker of esophageal cancer. Further studies are needed to confirm this finding.AcknowledgmentsNot applicable.The author(s) received no financial support for the research.Author contributionsHK corrected blood samples, interpreted the patient data, and was a major contributor in writing the manuscript. MT and YK recruited patients. The article was revised by MN and the final manu-script has been approved by all authors.Conflicts of interest statementThe authors declare that they are no conflicts of interest.References 1) National Cancer Center Japan: Statistical information of cancer in Japan. https://ganjoho.jp/reg_stat/statis-tics/stat/cancer/4_esophagus.html(Last Accessed June. 11, 2022) 2) Watanabe M, Toh Y, Ishihara R, et al: Comprehensive registry of esophageal cancer in Japan, 2014. Esoph-agus, 2022; 19: 1-26. 3) Hashimoto T, Kajiyama Y, Tsutsumi-Ishii Y, Nagaoka I, Tsurumaru M: Circulating micrometastases of esopha-geal cancer detected by carcinoembryonic antigen mRNA reverse transcriptase-polymerase chain reac-tion: clinical implications. Dis Esophagus, 2008; 21: 690- 696. 4) Nakamura S, Yagata H, Ohno S, et al: Multi-center study evaluating circulating tumor cells as a surrogate 374for response to treatment and overall survival in meta-static breast cancer. Breast Cancer, 2010; 17: 199-204. 5) Tol J, Koopman M, Miller MC, et al: Circulating tumour cells early predict progression-free and overall survival in advanced colorectal cancer patients treated with chemotherapy and targeted agents. Ann Oncol, 2010; 21: 1006-1012. 6) Cohen SJ, Punt CJA, Iannotti N, et al: Prognostic signif-icance of circulating tumor cells in patients with meta-static colorectal cancer. Ann Oncol, 2009; 20: 1223-1229. 7) Miller MC, Doyle GV, Terstappen LW: Significance of circulating tumor cells detected by the CellSearch® system in patients with metastatic breast colorectal and prostate cancer. J Oncol, 2010; 2010: 617421. 8) Okegawa T, Nutahara K, Higashihara E: Association of circulating tumor cells with tumor-related methylated DNA in patients with hormone-refractory prostate cancer. Int J Urol, 2010; 17: 466-475. 9) Coumans FAW, Ligthart ST, Terstappen LWMM: Interpretation of changes in circulating tumor cell counts. Transl Oncol, 2012; 5: 486-491.10) Sobin LH, Gospodarowicz MK, Wittekind C (eds.): International Union Against Cancer TMN Classifica-tion of Malignant Tumours 7th edition. 200911) Matsusaka S, Chin K, Ogura M, et al: Circulating tumor cells as a surrogate marker for determining response to chemotherapy in patients with advanced gastric cancer. Cancer Sci, 2010; 101: 1067-1071. 12) Lurje G, Schiesser M, Claudius A, Schneider PM: Circulating tumor cells in gastrointestinal malignan-cies: current techniques and clinical implications. J Oncol, 2010; 2010: 392652.13) Tarumi S, Gotoh M, Kasai Y, et al: Innovative method using circulating tumor cells for prediction of the effects of induction therapy on locally advanced non-small cell lung cancer. J Cardiothorac Surg, 2013; 8. 14) Makita H, Murakami M, Sawatani T, et al: Clinical significance of measurement of tumor markers for esophageal squamous cell carcinoma―a retrospective analysis in recurrent cases. Jpn J Gastroenterol Surg, 2004; 37: 1805-1812.15) Mei X, Zhu X, Zuo L, et al: Predictive significance of CYFRA21-1, squamous cell carcinoma antigen and carcinoembryonic antigen for lymph node metastasis in patients with esophageal squamous cancer. Int J Biol Markers, 2019; 34: 200-204.16) Turato C, Scarpa M, Kotsafti A, et al: Squamous cell carcinoma antigen 1 is associated to poor prognosis in esophageal cancer through immune surveillance impairment and reduced chemosensitivity. Cancer Science, 2019; 110: 1552-1563.17) Togo S, Katagiri N, Namba Y, et al: Sensitive detection of viable circulating tumor cells using a novel condi-tionally telomerase-selective replicating adenovirus in non-small cell lung cancer patients. Oncotarget, 2017; 8: 34884-34895.18) Qian H, Zhang Y, Xu J, et al.(2021): Progress and appli-cation of circulating tumor cells in non-small cell lung cancer. Mol Ther Oncolytics, 2010; 22: 72-84.Funding