title: Langerhans cell histiocytosis: 37 cases in a single brazilian institution.
abstract: OBJECTIVE
  To improve the level of 'definitive' diagnosis of Langerhans cell histiocytosis by immunohistochemical investigation of the CD1a surface antigen and to compare outcomes in respect to age, gender, stage of the disease, treatment response and level of diagnostic accuracy.
  
  
  METHODS
  A retrospective study was carried out of 37 children and adolescents with possible Langerhans cell histiocytosis between 1988 and 2008. The diagnoses were revisited using immunohistochemical investigations for CD1a, S-100 and CD68 in an attempt to reach definitive diagnoses for all cases.
  
  
  RESULTS
  Before the study, only 13 of 37 patients (35.1%) had a 'definitive' diagnosis; by the end of the study, this number rose to 25 patients (67.6%). All reviewed cases were positive for the CD1a antigen. Overall survival was 88.5%. Multisystem disease (Stage 2; n=19) and absence of response at the 6th week of therapy (n=5) were associated to significantly lower overall survival (p-value = 0.04 and 0.0001, respectively). All deaths occurred in patients with multisystem disease and organ dysfunction at diagnosis. Other potential prognostic factors were not significant. Reactivation episodes occurred in 75% of the patients with multisystem disease. Diabetes insipidus was the most common sequel (21.6%).
  
  
  CONCLUSIONS
  The level of diagnostic accuracy was increased through immunohistochemistry. The overall survival rate was similar to international multicentric studies. Multisystem disease and absence of response at six weeks of treatment were the most important unfavorable prognostic factors. The frequency of reactivation for patients with multisystem disease was higher than described in the literature, probably because maintenance chemotherapy was used only in two cases.
authors.affiliation: Hematology Service, Hospital das Clínicas, Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG, Brazil.
authors.forename: Luciana Terra
authors.initials: LT
authors.lastname: Babeto
authors.forename: Benigna Maria
authors.initials: BM
authors.lastname: de Oliveira
authors.forename: Lúcia Porto Fonseca
authors.initials: LP
authors.lastname: de Castro
authors.forename: Márcia Kanadani
authors.initials: MK
authors.lastname: Campos
authors.forename: Maria Thereza Macedo
authors.initials: MT
authors.lastname: Valadares
authors.forename: Marcos Borato
authors.initials: MB
authors.lastname: Viana