AKT1 and ductal breast carcinoma in situ: Although AKT1 mutations are rare in invasive breast cancer (approximately 2 %) (TCGA), activating AKT1 exon 2 mutations were observed in the in situ component of two of three breast tumours exhibiting the mutation in the invasive component in one study [69] and in three of six papillomas harbouring DCIS in another study [74].