title: S100A6 preferentially labels type C nevus cells and nevic corpuscles: additional support for Schwannian differentiation of intradermal nevi.
abstract: BACKGROUND
  Melanocytic nevi typically show a morphologic sequence of maturation from epithelioid "type A" cells to fusiform, Schwann cell-like "type C" cells with dermal descent. Nevi may also produce Wagner-Meissner-like structures (nevic corpuscles). Previous studies have shown that this maturation of intradermal nevi recapitulates intermediate stages in Schwann cell development. In intradermal nevi, we have evaluated the pattern of S100A6 protein, a form of S100 found in Schwann cells.
  
  
  METHODS
  Formalin-fixed, paraffin-embedded archival tissues were evaluated by immunohistochemistry using antibodies specific for S100A6 and S100B in 38 intradermal nevi (IDN). Ten neurofibromas (NF), 3 Schwannomas (SCH), 2 palisaded and encapsulated neuromas (PEN), and 2 granular cell tumors (GCT) were included as positive controls since these lesions have large numbers of Schwann cells.
  
  
  RESULTS
  Melanocytic nevi demonstrated preferential anti-S100A6 staining of "type C" cells (36/38; 28 strong, 8 weak) and nevic corpuscles (25/38; 19 strong, 6 weak) compared to "type A" cells (17/38; 17 weak) and "type B" cells (17/38; 4 strong, 13 weak). All NF, SCH, and PEN stained strongly with anti-S100A6. Both GCT were negative with anti-S100A6 but positive with anti-S100B.
  
  
  CONCLUSIONS
  The pattern of S100A6 expression in intradermal nevi further supports the hypothesis that maturation in these lesions recapitulates features of Schwann cell differentiation. The lack of S100A6 expression by both GCT suggests that these lesions have lost this feature of Schwann cells, which may play a role in their peculiar phenotypic appearance.
authors.affiliation: Department of Pathology, University of Michigan Hospitals, Ann Arbor, Michigan 48109-0602, USA. dfullen@umich.edu
authors.forename: D R
authors.initials: DR
authors.lastname: Fullen
authors.forename: J A
authors.initials: JA
authors.lastname: Reed
authors.forename: B
authors.initials: B
authors.lastname: Finnerty
authors.forename: N S
authors.initials: NS
authors.lastname: McNutt
mesh_terms: D018797:Cell Cycle Proteins; D002471:Cell Transformation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D018330:Nevus, Intradermal / Q000378:metabolism* / Q000473:pathology; D009508:Nevus, Pigmented / Q000378:metabolism* / Q000473:pathology; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins / Q000378:metabolism*; D012583:Schwann Cells / Q000378:metabolism* / Q000473:pathology; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: D018797:Cell Cycle Proteins; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; C055351:S100A6 protein, human