In addition to the role of activating FGFR3 mutations in a variety of cancers, germline-activating mutations in FGFR3 are the etiology of achondroplasia, the most common form of skeletal dwarfism in humans, and somatic activating mutations in FGFR3 cause seborrheic keratosis, a benign skin tumor, and epidermal nevi, a benign hyperplastic skin lesion (Hafner et al., 2006; Logie et al., 2005; Naski et al., 1996). This evidence concerns the gene FGFR3 and seborrheic keratosis.