In the tumor tissue, the mutational analysis revealed a p.(Hys1047Leu) PIK3CA mutation at 36.9% frequency, and the ctDNA NGS analysis validated the tissue mutation but also identified a second mutation in the ESR1 gene (p.(Asp538Gly), 0.39%), usually associated with endocrine resistance. The gene discussed is PIK3CA; the disease is neoplasm.