NF1 and schwannomatosis: Unlike plexiform neurofibromas, which most often arise within the context of classical NF1 and are virtually pathognomonic to NF1, most plexiform schwannomas are (at least initially) isolated/solitary, with only a few cases arising within the context of NF2-related schwannomatosis (NF2/MERLIN schwannoma predisposing syndrome) [1,4,9,24,25,26,27,28,29]; one must think, however, in the cases of truly isolated/solitary lesions (after extensive work-up), about mosaicism for the schwannomatoses genes (Table 7).