The authors assessment the heterogeneity in basal time (by baseline ultrasound-guide core biopsies from two distinct areas of each tumor), and this entity was defined as at least one of the six areas with either (1) HER2 positivity by ISH in more than 5% and <50% of tumor cells, or (2) a tumoral area with negative result for HER2. This evidence concerns the gene ERBB2 and neoplasm.