PIK3CA and carcinoma: In cancer, where constitutive PI3K/AKT signaling has long been identified as a recurrent driver axis [62,63], a more specific stem cell involvement can be deduced, e.g., from PIK3CA(H1047R) induced trans-conversion of luminal and basal cell layers of the mammary gland in mouse from which composed, multi-lineage carcinomas derive [64].