Penile neurofibromas

Unless omitted and underreported, penile neurofibromas are rare. Between January 2, 1982 and December 31, 1997 through the USF Regional Genetics Program we evaluated 566 propositi with suspected or clinically diagnosed neurofibromatosis (NF1, NF2, segmental NF=NF5, NF/Noonan syndrome, familial café-au-lait macules, and solitary neurofibroma, NF). These index cases were part of 32,715 families evaluated during the period. NF1 was the diagnosis in 361; 2 of them had penile NFs. A toddler presented with congenital plexiform NF of the penile shaft and another propositus developed two small subcutaneous NFs, on the penile shaft and on the left scrotal wall, respectively. A review documented 26 additional patients with penile NF. As to the pathogenesis of the NF1 lesions, a paracrine growth model including the multiple levels of regulation of expression of the NF1 gene appeared more plausible than the loss of heterozygosity (LOH) model, which ignores the complexity of the paracrine growth mechanism.