Whereas Shi and collaborators observed that higher somatic mutation frequency in the PIK3CA gene in the breast tissues of cases was associated with trastuzumab resistance[59], Lesurf et al. reported that no somatic or germline mutations were associated with response to trastuzumab in breast cancer tissues of cases compared to controls[58] [Supplementary Table 18]. The gene discussed is PIK3CA; the disease is breast cancer.