The missense mutation of c.3140A>G;p.H1047R at 1047 of exon 21 of PIK3CA gene was detected in the patient, which was recorded for 2852 times in the Catalogue of Somatic Mutations in Cancer database, including 1632 times for breast cancer, 434 times for colorectal cancer, 183 times for endometrial cancer, 110 times for ovarian cancer, and 72 times for soft tissue sarcoma. The gene discussed is PIK3CA; the disease is breast cancer.