Neurofibromatosis 1 : Diffuse Neurofibroma
Diffuse neurofibroma (DF) is an uncommon variant that is usually seen in the setting of Neurofibromatosis 1 but may also rarely occur sporadically. It frequently involves the head and neck region in children and young adults. The tumor is poorly-circumscribed and spreads laterally along tissue planes causing plaque-like thickening of the skin. In contrast to conventional (localized) neurofibromas which show low cellularity and Schwann cells with wavy, pointed nuclei, diffuse neurofibromas are hypercellular and are composed of short fusiform or round Schwann cells which are present in a background of fine fibrillary collagen. They frequently show organoid structures resembling Meissner corpuscles (pseudo-Meissnerian structures), mature fat, or large ectatic blood vessels.