title: Langerhans cell histiocytosis: an evaluation of histopathological parameters, demonstration of proliferation by Ki-67 and mitotic bodies.
abstract: OBJECTIVE
  Langerhans cell histiocytosis (LCH) is a disease with a variable clinical manifestation, being localised (SS) or disseminated (MS). The etiology and pathogenesis of LCH is unknown. It is a proliferative disorder of monoclonal origin, but not necessarily neoplastic. In our study we evaluated histopathological parameters and proliferative activity in LCH.
  
  
  METHODS
  Infiltrates from 43 patients with LCH were investigated (nSS=32, nMS=11). We evaluated different histopathological parameters semiquantitatively, demonstrating proliferation using immunohistochemistry for Ki-67.
  
  
  RESULTS
  Overall, the histopathological picture of LCH was heterogeneous. The degree of eosinophilia and presence of necroses was significantly higher in SS-infiltrates compared to MS-infiltrates. Mitotic figures were detected in more than half the infiltrates. The Langerhans origin was verified by CD1a. Ki-67 was highly expressed in all but one infiltrate.
  
  
  CONCLUSIONS
  The presence of necrosis and the degree of eosinophilia are related to SS-disease in our study. Ki-67 expression and the presence of mitotic figures indicate that local proliferation contributes to the accumulation of Langerhans cells. Supported by the histopathological appearance of the lesions and a level of Ki-67 expression lower than that of neoplastic tissue, we suggest that LCH is a reactive condition, possibly induced by immunostimulation caused by unknown agents.
authors.affiliation: Department of Pathology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Micha I
authors.initials: MI
authors.lastname: Bank
authors.forename: Pia
authors.initials: P
authors.lastname: Rengtved
authors.forename: Henrik
authors.initials: H
authors.lastname: Carstensen
authors.forename: Bodil L
authors.initials: BL
authors.lastname: Petersen
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D002455:Cell Division; D002648:Child; D004804:Eosinophils / Q000473:pathology; D006646:Histiocytosis, Langerhans-Cell / Q000473:pathology*; D006801:Humans; D019394:Ki-67 Antigen / Q000032:analysis*; D008214:Lymphocytes / Q000473:pathology; D008938:Mitosis; D009336:Necrosis; D010950:Plasma Cells / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen