ESR1 and breast cancer: Interestingly, the genomic pattern observed in patient #26 CTCs (i.e., a lobular BC with an expected E‐cadherin deleterious LOH mutation, accompanied by a subclonal, heterogeneous, mono‐and biallelic ESR1 LBD mutation, in the context of a one‐copy TP53 loss, Fig. 2) had been previously observed by us in a lobular BC patient from a different cohort [24].