A family of genes in which genetic variants have been found in multiple vascular malformations. Originally identified as an oncogene (the term is short for ‘rat sarcoma’) three subtypes were subsequently identified (HRAS, KRAS and NRAS) variants in all of which have been found in vascular malformations. RAS proteins are small GTPases which signal through the MEK/ERK pathway, but also into the PI3 Kinase pathway.