HRAS and phakomatosis pigmentokeratotica: The leading hypothesis for the origin of SLN involves a mosaic pattern of embryonic development with genetic variants, notably HRAS, responsible for the patchy or speckled appearance and tendency to respect the cutaneous lines of Blaschko [5]. Both conventional and phacomatosis pigmentokeratotica-associated SLN have been observed to exhibit a postzygotic activating HRAS genetic variant that over-activates the RAS-MAPK pathway [6]. However, secondary neoplasms within these lesions do not all show the same molecular mechanism of pathogenesis [7].