ERBB2 and breast neoplasm: In addition, nearly all breast tumours having EGFR and/or ErbB2 overexpression were contained in the IBC-rich sample cluster: 17 out of 33 EGFR and/or ErbB2-positive samples in the IBC-rich cluster versus 25 out of 26 EGFR- and ErbB2-negative samples in the IBC-poor cluster (Pearson χ2, P<0.0001; Figure 3B).