Further, significant differences were seen in the HER2 immunohistochemical status and HER2 status in the primary setting in patients with PIK3CA mutations in their relapse tumor as compared to those without mutations (p = 0.015 and p = 0.011, respectively; Supplementary Table S1 and Supplementary Fig. S3a-b). The gene discussed is PIK3CA; the disease is neoplasm.