Objective:To investigate the application value of carbon nanoparticle tracer in lymph node dissection for Siewert type Ⅱ and Ⅲ adenocarcinoma of esophagogastric junction (AEG).Methods:The retrospective cohort study was conducted. The clinicopathological data of 147 patients with Siewert type Ⅱ and Ⅲ AEG who were admitted to Shengli Petroleum Central Hospital from June 2015 to July 2020 were collected. There were 109 males and 38 females, aged (65±9)years. All the patients underwent laparoscopic-assisted radical resection of AEG via esophageal hiatus. Of 147 patients, 61 cases not injected with carbon nanoparticle tracer preoperatively were allocated into control group and 86 cases injected with carbon nanoparticle tracer preoperatively were allocated into experimental group. Observation indicators: (1) surgical and postoperative situations; (2) influencing factors analysis of No.10 lymph nodes metastasis. Measurement data with normal distribution were represented as Mean± SD, and comparison between groups was conducted using the t test. Count data were represented as absolute numbers or percentages, and comparison between groups was analyzed by the chi-square test. Univariate analysis was conducted by statistic methods based on data type, and multivariate analysis was conducted by the Logistic step-wise regression model. Results:(1) Surgical and postoperative situations. Patients of the experimental group and control group completed laparoscopic-assisted radical resection of AEG via esophageal hiatus successfully. There was no significant difference in the operation time, volume of intraoperative blood loss, the total number of lymph node dissection, the number of the first station, the second station and positive lymph nodes between the two groups ( P>0.05). For the experimental group, the black staining rate of lymph nodes was 57.937%(1 365/2 356), the black staining rate of the first station and second station lymph nodes was 77.989%(1 024/1 313) and 43.691%(232/531), the black staining rate of Siewert type Ⅱ and Ⅲ AEG patients was 56.855%(423/744) and 58.437%(942/1 612), respectively. The lymph node metastasis rate was 19.091%(815/4 269) of 147 patients, 18.573%(242/1 303)of Siewert type Ⅱ AEG patients and 19.319%(573/2 966) of Siewert type Ⅲ AEG patients. For Siewert type Ⅱ AEG patients, the metastasis rate of No.1, 2, 3, 4sa, 4sb, 7, 8a, 11p lymph nodes was more than 10%, the metastasis rate of No.4d, 5, 6, 9, 10, 11d, 12a lymph nodes was lower than 10%. For Siewert type Ⅲ AEG patients, the metastasis rate of No.1, 2, 3, 4sa, 4sb, 7, 8a, 10, 11p and lower mediastinal lymph nodes was more than 10%, the metastasis rate of No.4d, 5, 6, 9 11d, 12a and lower mediastinal lymph nodes was lower than 10%. There was no significant difference in the Clavien Dindo classification of postoperative complications between the two groups ( P>0.05). (2) Influencing factors analysis of No.10 lymph nodes metastasis. Results of multivariate analysis showed that tumor T staging and degree of tumor differention was an independent influencing factor for No.10 lymph nodes metastasis ( P<0.05). Conclusions:For Siewert type Ⅱ and Ⅲ AEG patients, the application of carbon nano-partide tracer can not increase the number of lymph node dissection. The second station lymph node dissection should be paid attention for Siewert type Ⅱ AEG. Tumor T staging and degree of tumor differentiation are independent influencing factors for No.10 lymph nodes metastasis.