Based on their occurrences in distinctly perfused vessel beds, a large range of vascular malformations can be categorized as either slow-flow “PIKopathies” that involve the PI3K/AKT/mTOR pathway or fast-flow “RASopathies,” involving a stimulation of the RAS/MAPK pathway (reviewed in ref. 22). This evidence concerns the gene PIK3CA and vascular malformation.