title: Nerve sheath tumours with hybrid features of neurofibroma and schwannoma: a conceptual challenge.
abstract: OBJECTIVE
  To characterize and delineate a subset of rare nerve sheath tumours showing hybrid features of neurofibroma and schwannoma.
  
  
  RESULTS
  Nine lesions were identified in the authors' files showing predominant features of neurofibroma with distinct, often nodular regions of classical schwannomatous differentiation. Most patients were adults, eight out of nine were male. Of the nine lesions, two were dermal, two were subcutaneous and five were subfascial. Five lesions had a plexiform architecture and one patient had overt neurofibromatosis. One out of six patients with follow-up developed local recurrence. Schwannoma-like regions displayed strong S100 staining, in contrast to more varied and limited S100 reactivity in neurofibromatous areas. The Antoni A areas could be quite cellular with high MIB-1 proliferation indices. No lesion underwent malignant change.
  
  
  CONCLUSIONS
  Our results demonstrate that some nerve sheath tumours may contain histologically clear components of both neurofibroma and schwannoma, suggesting that (despite evident and well-defined clinicopathological differences) these two lesions may be even more closely related than previously recognized. Whether this phenomenon results from a localized microenvironmental change or from a clonal genetic alteration remains unknown.
authors.affiliation: Department of Pathology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Feany
authors.forename: D C
authors.initials: DC
authors.lastname: Anthony
authors.forename: C D
authors.initials: CD
authors.lastname: Fletcher
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D034961:Antigens, Nuclear; D014408:Biomarkers, Tumor / Q000032:analysis; D002648:Child; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D019394:Ki-67 Antigen; D008297:Male; D008875:Middle Aged; D018396:Mucin-1 / Q000032:analysis; D018317:Nerve Sheath Neoplasms / Q000737:chemistry / Q000473:pathology*; D009442:Neurilemmoma / Q000737:chemistry / Q000473:pathology*; D009455:Neurofibroma / Q000737:chemistry / Q000473:pathology*; D016900:Neurofilament Proteins / Q000032:analysis; D009687:Nuclear Proteins / Q000032:analysis; D009418:S100 Proteins / Q000032:analysis
chemical_list: D034961:Antigens, Nuclear; D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D018396:Mucin-1; D016900:Neurofilament Proteins; D009687:Nuclear Proteins; D009418:S100 Proteins