ERBB2 and breast cancer: Finally, in the HER-2 positive BC subgroup, the existence of residual axillary disease was a poor prognostic factor and the magnitude of the risk was similar for patients with 1 to 3 nodes involved and those with 4 or more nodes involved (RFS HR 2.68 95% CI [1.63–4.41] vs. 2.67 95% CI [1.24–5.77]), though the interpretation might be limited by the weak effective of the latter category (n = 20 out of 295 HER-2 positive BC patients, 6.8%).