With regard to the type of mutations present in ILC, we observed that D538G is the most common mutation, present in the metastatic disease from 57.1%, 56.3%, and 60.0% of the ILC patients with ESR1-mutated metastases from our series, MSKCC-IMPACT, and the SoFEA/PALOMA-3 ctDNA, respectively. This evidence concerns the gene ESR1 and metastatic neoplasm.