ESR1 and neoplasm: Interestingly, when assessed by NGS in the entire HER2-2D cohort, 9 distinct tumor-specific alterations were detected in blood, for a total of 11 mutational hits in 11 different patients, as follows: ESR1 p.D538G, p.Y537C, and p.Y537S; PIK3CA p.E545K, p.H1047R (in two patients); TP53 p.A276D (in two patients), p.C141Y, p.R213*, and p.S240R.