NF1 and plexiform neurofibroma: Using both NF1 intragenic polymorphisms and markers from flanking and more distal regions of chromosome 17, Colman et al. demonstrated loss of heterozygosity (LOH) of the NF1 gene in eight neurofibromas from 22 patients and Serra et al. found LOH in 15 out of 60 dermal neurofibromas [55, 57].