ERBB2 and breast cancer: Limitations of the present study include: (i) the retrospective approach of molecular analyses, (ii) the exploratory subgroup analysis for BCs with lobular histology, (iii) exclusion of a small minority of cases with controversial subtype calls (including cases classifiably as BC with mixed ductal/lobular features) and (iv) the comparatively small absolute number of ERBB2-mutated cases.