Score plots of the partial least squares-discriminant analysis (PLS-DA) models illustrated a marked separation between the HC group and BC molecular subtypes by both ESI modes (Figure 3 and Figure S2); the “goodness” of the PLS-DA model, measured by R2 and Q2, showed that no over-fitting was observed and, consequently, these models are acknowledged for successful discernment between HC patients and the LA, LB, TN and HER2 BC molecular subtypes [30] (Table S1). The gene discussed is ERBB2; the disease is breast cancer.