ERBB2 and invasive ductal breast carcinoma: Current efforts in I-SPY2 involve expanding the study to an additional ~700 patients, which could facilitate comparisons of the clinical significance of ctDNA among groups within the HER2-positive (HR-negative/HER2-positive vs. HR-positive/HER2-positive) and histological (invasive lobular carcinoma vs. invasive ductal carcinoma) subtypes.