ERBB2 and breast cancer: To confirm this observation, the copy number status of the GSDMB locus was determined by FISH (Figure 2A) in a cohort of 53 breast cancer patients including HER2-positive (n = 29) and HER2-negative (n = 24) tumours classified according to the ERBB2 amplification status (“discovery series” in Supplementary Table 2).