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Ppin 70 lymph nodes in 17 patients.Micrometastasis to lymph nodesIn immunostaining with CK13, one micrometas-tasis was detected in one patient without evidence of lymph node metastasis on HE stain, and 16 micrometastases were detected in 9 patients who were determined to be metastasis-positive by HE stain. Therefore, 10 patients were evaluated as lymph node micrometastasis-positive. The main tumors stained positive for CK13 in all 25 cases. All lymph nodes that were found to be metastasized by HE stain also stained positive with CK13.Relationships between micrometastasis and pathological factorsThe micrometastasis-positive group included many cases with high pT and pN, advanced pStage, lymphatic and vascular invasion, and well-differen-tiated carcinoma (Table 1). A comparison based on VariableSexSiteAgeDepthLymph node metastasisAdvanced stageDifferentiationLymphovascular invasionVenous invasionIntramural metastasisUt: upper thoracic esophagus, Mt: middle thoracic esophagus, Lt: lower thoracic esophagus, T: tumor, N: lymph node, well: well-differentiated squamous cell carcinoma, mod: moderately differentiated squamous cell carcinoma, ly: lymphovascular invasion, v: venous invasion, IM: intramural metastasisT1/T2-3N1/N2-3Micrometastasis(+)/micrometastasis(-)pIM0/pIM1ly0-2/ly3v0-1/v2T: tumor, N: lymph node, IM: intramural metastasis, ly: lymphovascular invasion, v: venous invasionMale/FemaleUt/Mt, Lt<60 / ≥60pT1/pT2-pT3pN0-N1/pN2-N3pStage0-Ⅱ/pStageⅢ-Ⅳwell/modly0-2/ly3v0-1/v2IM0/IM1Table 2　Histopathologic factors and degree of differentiationTable 1　Patient backgroundNumber of patients23/23/2212/1311/1414/1111/1414/1120/515/1021/4Well differentiated2/123/118/610/410/45/9differentiated types showed that well-differenti-ated cases were likely to have more advanced tumors (Table 2). To investigate the factors related to micrometastasis, logistic regression analysis was performed with pStage and degree of differentia-tion as independent variables and micrometastasis as the dependent variable. This analysis showed a tendency for cases in pStage III or higher to be more likely to be micrometastasis-positive (odds ratio (OR): 6.6, confidence interval (CI): 0.8-54, p=0.08). The OR for well-differentiated tumors was 1.5 (CI: 0.2-12), but the p value of 0.71 indi-cated that the relationship between degree of differentiation and micrometastasis was not signifi-cant (Table 3).Long-term survivalPatients with micrometastasis to lymph nodes had shorter survival compared to those without micrometastases (p=0.002; Figure 1). There was Micrometastasis-Micrometastasis-positivenegative8/21/96/42/82/82/88/25/53/76/415/02/136/99/612/39/66/915/012/315/0Moderately differentiated9/27/42/911/010/110/10.150.6540.2840.0480.0030.0480.0480.0020.0120.0080.0010.0320.0480.0530.0850.005365