ERBB2 and gastric adenocarcinoma: Overall, the HER2 status concordance rate between the primary gastric adenocarcinoma tissue and CB-MEs was 88.9% (40/45); however, the concordance level between the two sample types was evaluated as poor (κ = − 0.056), since the five HER2-positive primary gastric adenocarcinoma and CB-ME samples were from five different individuals for whom the paired sample was negative.