title: True malignant histiocytosis.
abstract: OBJECTIVE
  To attempt to distinguish cases of true malignant histiocytosis from the clinical syndromes of so-called malignant histiocytosis with use of recent methods.
  
  
  METHODS
  We retrospectively studied the laboratory data and clinical course of Mayo patients who had clinical syndromes of so-called malignant histiocytosis and reviewed available paraffin-embedded tissue specimens to identify the nature of the malignant cells.
  
  
  METHODS
  After elimination of cases of infection-associated hemophagocytic syndrome, we reviewed and studied seven cases of so-called malignant histiocytosis in patients who had undergone assessment at Mayo Clinic Rochester between 1973 and 1993. We identified histiocytes by using current morphologic, cytochemical, and immunohistochemical methods. The clonal nature of the malignant cells was identified with morphologic, cytogenetic, and molecular genetic studies.
  
  
  RESULTS
  Only one of the seven cases had a true histiocytic origin. The malignant cells were T cells in three other cases (the cells were also CD30+ in two cases), CD30+ cells only in one case, epithelial cells in one case, and an undetermined cell type (stained positively only with antitrypsin) in one case.
  
  
  CONCLUSIONS
  True malignant histiocytosis is an exceedingly rare disease, and only a few reports have clearly identified the histiocytic origin of the malignant cells. Previously, the lack of monoclonal antibodies specific to histiocytes and the absence of techniques for performing molecular genetic studies on paraffin-embedded tissue prevented the study of such cases. With newer techniques cases of true malignant histiocytosis can now be identified.
authors.affiliation: Division of Hematopathology, Mayo Clinic Rochester, Minnesota 55905, USA.
authors.forename: W
authors.initials: W
authors.lastname: Mongkonsritragoon
authors.forename: C Y
authors.initials: CY
authors.lastname: Li
authors.forename: R L
authors.initials: RL
authors.lastname: Phyliky
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics; D001706:Biopsy; D002869:Chromosome Aberrations; D003937:Diagnosis, Differential; D006644:Histiocytes / Q000473:pathology; D054747:Histiocytic Sarcoma / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D006801:Humans; D007124:Immunoenzyme Techniques; D008198:Lymph Nodes / Q000473:pathology; D016612:Paraffin Embedding; D016133:Polymerase Chain Reaction; D012189:Retrospective Studies
chemical_list: D014408:Biomarkers, Tumor