ERBB2 and breast cancer: Untargeted metabolomic analyses were performed using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS), gas chromatography quadrupole time-of-flight mass spectrometry (GC-QTOF-MS), and amino acid profiling to identify discriminant metabolites among the main BC subtypes, Luminal A (LA), Luminal B (LB), basal-like (BL), and HER2, as well as across different tumor stages (I, II, III, and IV) and a healthy control group.