Pattern of lymph node metastasis in thoracic esophageal squamous cell carcinoma with poor differentiation

The aim of the present study was to explore the pattern of lymph node metastasis (LNM) in poorly-differentiated esophageal squamous cell carcinoma (pdESCC) and the implication of postoperative irradiation. A total of 690 patients with pdESCC were retrospectively investigated. The rates of intro-thoracic and extra-thoracic LNM in pdESCC were investigated and compared to previous research on ESCC en bloc. The comparison of the rates between pdESCC and ESCC were performed using the Cochran-Mantel-Haenszel test. The clinicopathological factors associated with LNM in pdESCC were analyzed by Chi-squared tests, and Fisher's exact test was used to assess the rate difference of extra-thoracic LNM. Logistic-regression analysis was used to explore risk factors associated with lymph node (LN) station. Results demonstrated that the distribution pattern of LNM in pdESCC was significantly different compared with that of ESCC (P<0.05). Univariate and multivariate analysis indicated that risk factors associated with LNM were depth and length (P<0.001 and P<0.001) and multivariate analysis also indicated that the location of the tumor (P=0.042) was a risk factor associated with LNM in pdESCC. Metastasis in the abdominal cavity was significantly higher than in the neck in the middle and lower thoracic pdESCC (both P<0.01). LN station 102 and 7 for upper thoracic ESCC, 101 and 105 for middle thoracic ESCC, and 100 for lower thoracic ESCC were identified as high-risk stations for metastases in pdESCC compared to ESCC. Several parameters, including location and neck metastasis, were identified as risk factors of metastasis for the above sites, respectively. In conclusion, postoperative therapy should include more LN stations in pdESCC depending on risk factors of tumor metastasis individually.