Cutaneous mosaic RASopathies associated with rhabdomyosarcoma.

Variants in RAS are known drivers of certain pediatric blood and solid cancers, including brain tumors. Though most RAS-driven cancers are thought to occur sporadically, genetic syndromes caused by germline RAS variants portend a slightly higher risk of rhabdomyosarcoma (RMS) development. Three new cases and a review of the literature demonstrate that in rare cases, certain somatic RAS variants are associated with an increased risk of RMS and that RMS development may be heralded by the presence of concomitant RAS-driven birthmarks. Further prospective studies are needed to establish incidence and recommend appropriate monitoring guidelines for patients at risk.