High-throughput RNA sequencing and tumor resequencing have revealed that hyperactivating mutations in the PI3K signaling pathway occur in a substantial percentage of breast cancers.7 The PIK3CA gene itself, encoding the p110α catalytic subunit, is the most frequently mutated gene in breast cancer,8, 9 with mutations in 25–40% of all breast cancers.10, 11 However, the prognostic implications of p110α mutations remain unclear. The gene discussed is PIK3CA; the disease is breast cancer.