ERBB2 and breast cancer: CD63 staining was identified in 25% of TNBC (19/77), 22% (14/63) of ER+HER2−, 38% (18/47) of ER−HER2+, 74% (23/31) ER+HER2+ breast cancer cases (Figure 1H(i); Supplementary Figure S1B) (Chi-square p < 0.0001), possibly helping to hypothesise that the observed significantly higher number of EVs in sera of ER+HER2+ BC patients may reflect a higher number of tumour-derived EVs.