ERBB2 and ductal breast carcinoma in situ: Using the Smart-3SEQ data, we first observed a correlation between HER2 normalized gene expression and the average HER2-FISH signal/cell per DCIS region (r = 0.62, p < 0.0001) (Fig. 1d), suggesting that HER2 overexpression in our samples is significantly correlated with HER2 amplification.