Mixed Histology Is a Risk Factor for Lymph Node Metastasis in Early Gastric Cancer

Background: The risk factors of lymph node (LN) metastasis are important factors to consider in endoscopic submucosal dissection in early gastric cancer (EGC). The aim of the study was to identify the correlation between mixed histology and LN metastasis in EGC. Methods: A total of 1645 patients who underwent curative radical gastrectomy for EGC were divided into three groups (pure differentiated [pure D], mixed, and pure undifferentiated [pure UD]) according to histologic type. They were subsequently analyzed retrospectively for LN metastasis. The patients who had mixed histology between differentiated and undifferentiated tubular adenocarcinoma were defined as mixed group. Results: The pure UD group was significantly younger than the other groups. Tumor size was larger in the mixed group. LN metastasis occurred more frequently in the mixed group and the pure UD group than in the pure D group (pure D, mixed, and pure UD, 7.7%, 23.2%, and 10.8%, respectively; P < 0.001). A logistic regression analysis revealed that the independent risk factors for LN metastasis were large tumor size (odd ratio [OR], 1.308), submucosal invasion (OR, 3.565), lymphovascular invasion (OR, 9.755), and histologic types of mixed (OR, 2.360) and pure UD (OR, 1.657). Conclusions: Mixed histology is an important risk factor for LN metastasis in EGC. Thus, radical gastrectomy should be considered in the cases of mixed-type histology after endoscopic resection. (C) 2018 Elsevier Inc. All rights reserved.