Based on these observations, eight samples—including three ERα‐P (P43/P35/P50), four ERα‐C (C5/C6B/C11/C12) and one ERα‐N (N30)—with an immune cell dominated proteomic signal and with low tumour cell content were excluded for further analysis (Fig. S2C,D). This evidence concerns the gene ESR1 and neoplasm.