Pathologic definition and number of lymphovascular emboli: impact on lymph node metastasis in endoscopically resected early gastric cancer.

Endoscopic submucosal dissection (ESD) is widely accepted as an appropriate treatment modality for early gastric cancer (EGC). Accepted indications for ESD are mostly based on the risk of lymph node (LN) metastasis in EGC. The presence of lymphovascular emboli (LVEs) is the most important risk factor for predicting LN metastasis, but the criteria for diagnosing LVEs are inconsistent and controversial. Here, we defined LVE as the presence of tumor cells within a space according to the following criteria: (1) red cells or lymphocytes surrounding the tumor cells, (2) an endothelial cell lining, and (3) attachment to the vascular wall. We reviewed a series of 102 patients with EGC who underwent gastrectomy after ESD, evaluated the definition of LVE, counted the number of LVEs in ESD specimens, and validated the significance of the definition and number of LVEs with regard to the presence of LN metastasis in gastrectomy specimens using receiver operating characteristic (ROC) curve analysis. Overall, 13 instances (12.7%) of LN metastasis were identified among 102 patients with EGC who underwent gastrectomy after ESD. The LN metastasis-positive group showed higher numbers of definite (4.46 ± 2.45 versus 0.19 ± 0.07), suspicious (3.15 ± 0.76 versus 0.62 ± 0.14), and probable (1.62 ± 0.43 versus 0.43 ± 0.10) LVEs in ESD specimens than the LN metastasis-negative group. In ROC analysis, the area under the ROC curve was 0.851 (95% confidence interval [CI], 0.711-0.991) for definite LVEs, compared with 0.82 (95% CI, 0.698-0.960) for suspicious LVEs and 0.72 (95% CI, 0.549-0.891) for probable LVEs. We recommend the use of strict LVE criteria to predict LN metastasis and determine the need for surgical intervention after ESD.