The identification of a somatic (tumour) PIK3CA gene variant in a patient with metastatic oestrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative breast cancer who has progressed on endocrine therapy has implications for the clinical management of the current cancer.

Genomic testing in breast cancer may affect clinical management of the current cancer and management of the patient’s future cancer risk and that of their relatives.