ERBB2 and gastric cancer: We conclude that for distal gastric cancer location and for the diffuse subtype where HER2 positivity in general is less common (Baretton et al. 2019; He et al. 2015; Huang et al. 2013; Koopman et al. 2015; van Cutsem et al. 2015; Yoon et al. 2012; Barros-Silva et al. 2009; Cappellesso et al. 2015; Cho et al. 2013; Chua and Merrett 2012; Gomez-Martin et al. 2013; Gómez-Martin et al. 2012; Grabsch et al. 2010) weak HER2 expression and intratumoral heterogeneity account for more deviating test results.