LAUSR

DEAR EDITOR, The role of HRAS mutations in the pathogenesis of various human cancers is well established. Recent studies indicate that cutaneous nevi can also harbour HRAS, KRAS and NRAS mutations and this group of RAS-mutation positive birthmarks has been referred to as the mosaic RASopathies. In a subset of cases, these segmental and Blaschkoid nevi may be associated with benign or malignant neoplasms of other organ systems containing the same genetic mutation. There is a growing literature reporting rhabdomyosarcoma in association with mosaic RASopathies. KRAS mutations have been reported in association with phakomatosis pigmentokeratotica and rhabdomyosarcoma in the same patient. Congenital melanocytic nevi (CMN) are known to be caused by NRAS mutations. Rhabdomyosarcoma has also been reported in at least six patients with CMN, although genetic testing of NRAS was not performed in these cases. Somatic mutations and