title: Incipient corneoscleral xanthogranuloma with S-100 positivity in a teenager.
abstract: OBJECTIVE
  To present a case of a corneoscleral juvenile xanthogranuloma (JXG) with diagnostically challenging features.
  
  
  METHODS
  A 15-year-old boy's small corneoscleral mass of recent onset was examined histologically and immunohistochemically.
  
  
  RESULTS
  The biopsy had some superficially misleading histological and immunohistochemical features: S-100 positivity (however, observable in 30% of JXG lesions) and lack of Touton giant cells (often absent in early lesions). Most importantly, the histiocytes stained negatively for CD1a and strongly positively for both lysozyme and CD68 antigen.
  
  
  CONCLUSIONS
  JXG is a benign histiocytic disorder that usually appears early in childhood but is also encountered in 13%-18% of cases in the second decade. The histiocytes usually stain positively for CD68 and negatively for S-100 and CD1a. Correctly distinguishing JXG from the more aggressive spectrum of Langerhans cell diseases (100% have CD1a positivity) is essential for patient treatment.
authors.affiliation: Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Kanoff
authors.forename: Kathryn
authors.initials: K
authors.lastname: Colby
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Jakobiec
mesh_terms: D000293:Adolescent; D015703:Antigens, CD / Q000378:metabolism; D018949:Antigens, CD1 / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D003316:Corneal Diseases / Q000175:diagnosis* / Q000378:metabolism; D006644:Histiocytes / Q000378:metabolism; D006801:Humans; D008297:Male; D009113:Muramidase / Q000378:metabolism; D009418:S100 Proteins / Q000378:metabolism*; D015422:Scleral Diseases / Q000175:diagnosis* / Q000378:metabolism; D014972:Xanthogranuloma, Juvenile / Q000175:diagnosis* / Q000378:metabolism; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D018949:Antigens, CD1; D015214:Antigens, Differentiation, Myelomonocytic; D009113:Muramidase; D009418:S100 Proteins; C419393:CD1a antigen; C067980:CD68 antigen, human; D000097382:CD68 Molecule