Fig. 1

Examples of HER2 fluorescence in situ hybridization (FISH) images corresponding to breast cancers, which were reclassified by 2018 ASCO/CAP guidelines. HER2, Spectrum Orange and CEP17, Spectrum Green. a A case from group 2: HER2/CEP17 ratio ≥2.0; average HER2 copy number <4.0 with a negative HER2 immunohistochemical stain (IHC), classified as negative by 2018 guidelines. b A case from group 3: HER2/CEP17 ratio <2.0; average HER2 copy number ≥6.0 with negative IHC, classified as negative by 2018 guidlines. c A case from group 4: HER2/CEP17 ratio <2.0; average HER2 copy number ≥4.0 and <6.0 with positive IHC, classified as positive by 2018 guidelines. d A case from group 4: HER2/CEP17 ratio <2.0; average HER2 copy number ≥4.0 and <6.0 with equivocal IHC, classified as negative by 2018 guidelines