ERBB2 and breast cancer: The clinical nodal positivity rate was numerically higher in the HER2-low group (55.0%) than in the HER2 IHC score 0 group (46.6%; P = 0.011) and, by extension, distribution of clinical stage (I versus II versus III) followed a similar pattern with a greater proportion of stage III breast cancers among the HER2-low group (P = 0.023).