PIK3CA and ductal breast carcinoma in situ: Mutations in the PIK3CA gene have been detected in both in situ and invasive matched breast samples [58]; however, the lower frequency or absence of PIK3CA mutation detected in the invasive component of some matched DCIS and IBC samples suggested that PIK3CA mutation is most likely an early event in breast tumorigenesis and is unlikely to play a role in DCIS progression [58].