Two cases harbored both shared and ctDNA only mutations for the same gene (patient-8: ESR1; patient-12: PIK3CA): the shared mutation had a higher AF than the ctDNA only mutations in both cases (ESR1: twofold; PIK3CA: threefold), suggesting that ctDNA only mutations occur in less represented clones that may not be detected in a single tumor biopsy, consistent with clonal heterogeneity. Here, ESR1 is linked to neoplasm.