Is A Plexiform Neurofibroma Pathognomonic of Neurofibromatosis Type I?

OBJECTIVES/HYPOTHESIS: Several prominent textbooks have claimed that a plexiform neurofibroma is pathognomonic for neurofibromatosis type I. This is not in agreement with the National Institutes of Health criteria, which require two signs to be present, one of which can be a plexiform neurofibroma. Is a plexiform neurofibroma pathognomonic for neurofibromatosis type I? STUDY DESIGN: Retrospective chart review. METHODS: Fifty-one patients with surgically resected plexiform neurofibromas between the years 1991 and 2001 were identified, and their charts reviewed. The presence and absence of any manifestation of neurofibromatosis type I as detailed in the National Institutes of Health criteria were recorded. The pathology database at the Hospital for Sick Children (HSC) was searched retrospectively. RESULTS: Five of the 51 patients had a single solitary plexiform neurofibroma. They were followed at the neurofibromatosis clinic at the HSC with regular detailed examinations and no other stigmata were found. CONCLUSION: Although plexiform neurofibromas are highly suggestive of neurofibromatosis type I, they are not pathognomonic as claimed.