Esophageal cancer is a common malignant tumor that seriously threatens human health, accounting for the 5th place in male cancer incidence and mortality [1], and China is a country with a high incidence of esophageal cancer and there is an obvious geographical distribution, the incidence rate in the high incidence area can be more than 100/100,000, and more than 90-95% of the tissue type is squamous cell carcinoma. Surgery is the first and only possible treatment for esophageal cancer. However, when patients visit the doctor with dysphagia symptoms, most of them are already in the progressive stage and have lost the chance of surgical cure. In recent years, despite the progress of surgery and other treatments, the overall 5-year survival rate of esophageal cancer still hovers around 10%. Therefore, for the surgical treatment of esophageal cancer, the degree of complete surgical resection and the quality of lymph node dissection are the key factors affecting the postoperative survival of patients. 1.Staging progress of esophageal cancer The esophagus travels through three anatomical regions: neck, chest and abdomen, adjacent to many important organs, and there is rich lymphatic traffic in its submucosa, which makes esophageal cancer present more jumping metastases and extensive regional lymph node metastases [4], therefore, the surgical treatment of esophageal cancer is different from other solid tumors with many methods, variable surgical paths and inconsistent lymph node clearance. Therefore, the surgical treatment of esophageal cancer is different from other solid tumors in that there are many different methods, variable surgical routes, and the scope of lymph node dissection. The TNM staging criteria for esophageal cancer developed by the International Union Against Cancer (UICC) are based on the depth of tumor infiltration (T), lymph node invasion (N) and distant metastasis (M), and are the most widely used international staging criteria to standardize clinicopathological staging, guide treatment decisions, determine patient prognosis and compare efficacy. The 6th edition of the TNM staging criteria for tumors [5, 6] was published by UICC and AJCC in 2002, and the lymph node metastasis grading (N) of esophageal cancer was divided into N0 (no regional lymph node metastasis) and N1 (regional lymph node metastasis). One is that recent studies have found that lymph node metastasis in esophageal cancer is the most important factor affecting patients’ long-term survival after surgery, and it is closely related to the degree of lymph node metastasis, i.e., the number of lymph nodes. Secondly, the criteria developed by European and American scholars are mainly based on the data of esophageal cancer patients in the West, which is dominated by adenocarcinoma and is different from the proportion of esophageal cancer cell types in Asian countries (squamous esophageal cancer accounts for more than 90%-95%), and thus cannot meet the staging and treatment needs of esophageal cancer patients in Asian countries, which are mainly squamous cancer. In view of this, the AJCC began to include Asian esophageal squamous cancer cases and invited Asian scholars to participate in staging when revising the TNM staging criteria for esophageal cancer [7, 8], and the new TNM staging criteria for esophageal cancer were published in 2009 and implemented worldwide in 2010 [9]. The most obvious change of the new TNM staging criteria is the unified naming and grouping of regional lymph nodes in esophageal cancer and the change of N classification of lymph node metastasis into N0~3 according to the number of lymph node metastasis, which corresponds to 0, 1~2, 3~6 and more than 6 lymph node metastasis respectively [10], which better reflects the role of this most important prognostic factor in esophageal cancer staging, which will have a profound impact on lymph node dissection in esophageal cancer. This will have a profound impact on the standardization of lymph node dissection and recording methods for esophageal cancer. The new TNM staging criteria do not require a rigid number of radical lymph node dissection for esophageal cancer. In principle, they require dissection of as many regional lymph nodes as possible, but the surgical complications must be controlled. Obviously, the higher the number of lymph nodes cleared, the less likely metastatic lymph nodes will be missed. Therefore, the determination of negative lymph nodes (N0) must be based on a certain number of resected lymph nodes to be reliable. The 6th edition of TNM staging for esophageal cancer specifies that at least 6 lymph nodes should be cleared, and studies have shown that this threshold is more accurate for N staging than clearing less than 6 lymph nodes [11~13]. However, as the importance of the metastatic pattern of esophageal cancer lymph nodes and the number of metastatic lymph nodes on the prognosis of esophageal cancer is gradually recognized [14, 15], the minimum number of lymph nodes required for radical lymph node dissection has increased, and different authors have proposed different lymph node dissection thresholds based on their own findings, such as Ikimura suggested 10, Yang suggested 18, and Peyre suggested 23 [16~18], Groth prospectively observed the treatment and follow-up results of 4882 progressive esophageal cancers and divided the number of lymph node clearances into 4 groups such as 0, 1~11, 12~29 and ³30, and found that only clearing lymph nodes ³12 showed significant survival improvement, while ³30 showed more significant improvement [19], in addition, the Rice et al., one of the leaders of this TNM standard, analyzed the data collected from 4627 esophageal cancer cases and found that the depth of invasion of esophageal cancer T was closely related to the degree of lymph node metastasis in its region, so the number of lymph node dissection should be adjusted according to the depth of invasion of the lesion: at least 10 lymph nodes should be removed for T1 tumors, 20 for T2 tumors, and at least 30 for T3/4 tumors [20]. . In addition to the above considerations, the new TNM staging of esophageal cancer recommends the removal of at least 12 regional lymph nodes based on a detailed study of a large number of cases by Dutkowski, who found that the diagnostic sensitivity of lymph node metastasis in esophageal cancer increases sharply with the increase in the number of lymph nodes removed, reaching a sensitivity of more than 90% after 12 lymph nodes, after which increasing the number of lymph nodes removed has limited improvement in sensitivity. Therefore, the new TNM staging criteria not only require at least 12 lymph nodes to be cleared, but also point out that “regional lymph nodes of the esophagus should be cleared as thoroughly as possible, but the resulting surgical complications must be controlled” [9]. 3. Technical issues of lymph node dissection in esophageal cancer: scope, count and surgical route In addition to the number of lymph nodes required for lymph node dissection in esophageal cancer, the regional aspects of lymph node dissection should also be taken into account. As mentioned above, the anatomical course of the esophagus is extensive, and the lymphatic drainage is also extensive, so it is necessary to identify the regional lymph nodes of the esophagus. It is not enough to remove only one or several groups of lymph nodes to fulfill the minimum number requirement. The TNM staging criteria for stage 7 esophageal cancer have modified the N classification, and the staging according to the number of metastatic lymph nodes is a significant improvement over the previous one, but ignoring the site or extent distribution of metastatic lymph nodes is still a major shortcoming, because the prognostic significance of a fixed number of positive lymph nodes concentrated in one area is different from that of multiple areas [22, 23]. In radical lymph node dissection, all lymph nodes in the esophageal region should be the target of dissection, rather than just the number requirement. It has been found that the lymph node metastasis of esophageal cancer is most likely to occur along the paraesophageal à pancreatic gastric lesser curvature à paragastric left artery à parietal celiac artery pathway and the metastatic pathway along the laryngeal retrolateral nerve chain to the cervical lymph nodes on both sides of the paraesophagus. Therefore, the Ivor-Lewis approach via the upper abdomen and right thorax has become an increasingly popular choice for the treatment of middle and lower esophageal cancer, especially gastroesophageal junction cancer, and is recommended in the new version of the Guidelines for the Standardized Treatment of Esophageal Cancer in China [24]. Despite the great technical progress in recent years, lymph node dissection of the upper mediastinum and neck along the laryngeal retrolateral chain and its consequent cervical anastomosis are still associated with high complications and significantly affect patients’ quality of life, thus it is controversial whether every patient and patients with upper esophageal cancer should undergo three-field lymph node dissection. For example, patients with early-stage or superficial esophageal cancer with few lymph node metastases may not benefit from three-field lymph node dissection [25], and patients with progressive esophageal cancer with extensive lymph node metastases are considered to have systemic disease in the West, and there is a lack of controversy over the advantages and disadvantages of radical lymph node dissection versus limited resection + radiochemotherapy. It can be said that the procedure with higher postoperative complications in esophageal cancer is esophageal neck anastomosis + radical three-field dissection. In order to balance radicality and complications, selective three-field lymph node dissection has recently been proposed as a better solution, i.e., using neck ultrasonography to guide the dissection, and performing three-field dissection if there are enlarged neck lymph nodes, while not emphasizing the need to perform radical three-field dissection if there are no enlarged neck lymph nodes radical triple field clearance [24, 26], but this recommendation is yet to be supported by large sample size prospective studies. The issue of lymph node counting has also become important after the change in N-staging to the number of lymph node metastases. In clinical practice, we often encounter the problem of multiple metastatic lymph nodes that are enlarged and fused, and while it is not a problem to determine the presence of lymph node metastases, it becomes difficult to distinguish how many lymph nodes are metastatic [27]. Another common situation is the fragmentation of lymph nodes during the clearance process, if not indicated and sent with the specimen, the number of lymph nodes will be overestimated and make the TNM incremental stage; therefore, the fragmented lymph nodes in this case should be bagged separately and sent for examination after indicating that they are individual lymph nodes. In the author’s unit, the lymph nodes of each group and their numbers are printed on self-adhesive labels on a trial basis, and the labels are attached with the bagging during surgery, which is not only less prone to errors, but also conducive to the supervision of bystanders to remind the inspection not to miss possible regional lymph nodes, which can be used as a reference. 4.The scope of lymph node dissection of esophageal cancer and surgical complications Radical lymph node dissection of esophageal cancer is a large and traumatic operation, which requires fine dissection to expose many important organs such as trachea, aorta, pulmonary vessels, retrograde laryngeal nerve, thyroid perineum, cervical macrovascular nerve, thoracic duct, abdominal cavity artery and its branches, etc. In addition, many patients have preoperative coexisting heart or lung lesions, so postoperative complications are very common [28 ], with the progress of surgical techniques, surgical instruments and anesthesia technology, the rate of postoperative complications in esophageal cancer is decreasing but ultimately cannot be completely avoided. Based on their larger data, Chen et al. found that within a certain number range (10-50), the rate of postoperative complications in esophageal cancer was not associated with an increase in the number of lymph nodes dissected, while the esophageal anastomosis site and the personal skill of the surgeon were independent prognostic factors [29]. The anastomosis site is determined according to the location of the esophagus where the tumor is located and cannot be changed at will, but one can improve the surgical technique and the use of innovative machinery such as ultrasonic knife so as to obtain radical lymph node dissection without increasing the incidence of surgical complications. 5.Outlook With the deepening understanding of the law of esophageal cancer lymph node metastasis and the rapid progress of surgical and anesthesia techniques, radical lymph node dissection for esophageal cancer has now been standardized [24]. Meanwhile, the application of various preoperative assessment measures and the use of lymphatic tracers during lymph node dissection are conducive to the complete dissection of regional lymph nodes in the esophagus. Also, the effect of surgical removal of a patient’s negative lymph nodes on the body is not known if the patient has no lymph node metastases. It is believed that preserving these negative lymph nodes can form a trap for tumor cells during later recurrence of esophageal cancer, which is conducive to early detection of tumor cells when they recur and metastasize and actively pursue the next step of treatment [30]. On the other hand, modern lymphatic contrast technology is developing rapidly, and if the contrast agent that can specifically show esophageal cancer metastasis and thus perform targeted lymphatic node dissection will be more targeted for maintaining radicality and reducing the incidence of postoperative complications in esophageal cancer.