ESR1 and invasive breast carcinoma: Additionally, transcripts encoding for markers of prognostic value in BrCa, such as KI67 (a marker of proliferation Ki‐67) and estrogen receptor alpha (ER) (Duffy et al., 2017), were differentially detected in both HER2+ (PMB2.8 and PMB2.36) and HER2‐ samples (PMB2.30 and PMB2.26) (Figure 3b; Plasma) in line with tissue biopsy data (Figure 3b; Tissue/Protein).