ERBB2 and neoplasm: Besides pre-analytic technical issues, such as HER2 IHC signal intensity decreasing over time [35], and IHC performed on old sections stored for more than 6 weeks [23], other biologic factors including intra-tumor genomic heterogeneity, co-amplification/polysomy 17 and monosomy 17 may contribute to this phenomenon [32, 36–43].