title: S100A6 expression in fibrohistiocytic lesions.
abstract: BACKGROUND
  S100A6, an S100 calcium-binding protein, has been found in a variety of cutaneous and extracutaneous lesions including: melanocytic nevi, melanoma, some salivary gland and epithelial tumors, and malignant fibrous histiocytoma (MFH). Dermal dendrocytes (DD) in the papillary dermis of skin also express S100A6 protein. We evaluated a variety of cutaneous fibrohistiocytic lesions to determine if the immunophenotype of S100A6 positivity can be expanded to include some or all of these lesions.
  
  
  METHODS
  Formalin-fixed, paraffin-embedded tissues from fibrous papules (FP, 20), dermatofibromas (DF, 20), dermatofibrosarcoma protuberans (DFSP, 5), atypical fibroxanthomas (AFX, 5), oral fibromas (3), digital fibroma (1), and dermatomyofibroma (1) were evaluated with antibodies to S100A6, S100B, factor XIIIa, and MAC387 using a one-hour capillary action-based immunohistochemical procedure.
  
  
  RESULTS
  DD in 20/20 FP, 19/20 DF, and 4/4 fibromas stained positively with anti-S100A6 in a pattern similar to anti-factor XIIIa. No DFSP cases stained with anti-S100A6. Anti-S100A6 showed superior staining to anti-factor XIIIa in 4/5 AFX cases.
  
  
  CONCLUSIONS
  The immunophenotypes of some fibrohistiocytic lesions can be expanded to include S100A6 protein. With the exception of AFX, the use of anti-S100A6 does not appear to offer added benefit over anti-factor XIIIa in the differential diagnosis of fibrohistiocytic lesions.
authors.affiliation: Department of Pathology, University of Michigan Hospitals, Ann Arbor, Michigan, 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: D000911:Antibodies, Monoclonal / Q000378:metabolism; D018797:Cell Cycle Proteins; D018223:Dermatofibrosarcoma / Q000378:metabolism / Q000473:pathology; D020405:Dermis / Q000294:innervation / Q000378:metabolism / Q000473:pathology; D003937:Diagnosis, Differential; D018219:Histiocytoma, Benign Fibrous / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008465:Mechanoreceptors / Q000378:metabolism / Q000473:pathology; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins / Q000032:analysis / Q000378:metabolism*; D017444:Skin Diseases, Papulosquamous / Q000378:metabolism / Q000473:pathology; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology; D011503:Transglutaminases / Q000378:metabolism; D014973:Xanthomatosis / Q000378:metabolism / Q000473:pathology
chemical_list: D000911:Antibodies, Monoclonal; D018797:Cell Cycle Proteins; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; C055351:S100A6 protein, human; D011503:Transglutaminases