Background Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) is an important cancer stem cell marker in gastric cancer. However, no detailed studies are available on LGR5 expression in poorly differentiated gastric adenocarcinoma (PD-AC). Therefore, we investigated the relationship between LGR5 expression and clinicopathological data in PD-AC. Methods LGR5 expression was identified in 41 PD-AC cases using RNAscope, which is a highly sensitive RNA in situ hybridization method. Epstein–Barr virus (EBV) infection was also detected by EBV in situ hybridization. Results LGR5 expression was identified in 38 of 41 PD-AC cases, and 17 cases were identified as LGR5 high. The frequency of EBV positivity tended to be higher in the LGR5 -low group than in the LGR5 -high group (P=0.0764). Furthermore, the frequency of vascular invasion tended to be higher in the LGR5 -high group than in the LGR5 -low group (P=0.0764). The overall survival of PD-AC patients in the LGR5 -high group was significantly lower than in the LGR5 -low group (log-rank test, P=0.0108). The Cox proportional hazard regression model revealed that the LGR5 -low group (HR=0.29; 95% CI: 0.11–0.74; P=0.01) showed independently better OS for PD-AC. Conclusions The correlation between high LGR5 expression and poor prognosis in PD-AC may be applicable to the development of LGR5 targeted therapy and prognostic markers. Further study is warranted.

Background Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) is an important cancer stem cell marker in gastric cancer. However, no detailed studies are available on LGR5 expression in poorly differentiated gastric adenocarcinoma (PD-AC). Therefore, we investigated the relationship between LGR5 expression and clinicopathological data in PD-AC.Methods LGR5 expression was identified in 41 PD-AC cases using RNAscope, which is a highly sensitive RNA in situ hybridization method. Epstein–Barr virus (EBV) infection was also detected by EBV in situ hybridization.Results In PD-AC, LGR5 expression was identified in 38 of 41 cases, and 17 cases were identified as LGR5 positive. The frequency of EBV positivity tended to be higher in the LGR5-negative group than in the LGR5-positive group (P = 0.0764). Furthermore, the frequency of vascular invasion tended to be higher in the LGR5-positive group than in the LGR5-negative group (P = 0.0764). A significant difference was found in overall survival (OS) between PD-AC cases in the LGR5-positive group and LGR5-negative group (log-rank test, P = 0.0108). The Cox proportional hazard regression model revealed that the LGR5-negative group (HR = 0.29; 95% CI: 0.11–0.74; P = 0.01) showed independently better OS for PD-AC.Conclusions The correlation between LGR5 positivity and poor prognosis in PD-AC may be applicable to target therapy for LGR5 and prognostic markers. Further study is warranted.