title: Histiocytic sarcoma with secondary involvement of the skin and expression of CD1a: evidence of indeterminate cell differentiation?
abstract: BACKGROUND
  Histiocytic sarcoma is an exceedingly rare malignant neoplasm composed of cells with a monocyte/macrophage phenotype. In the current nosology of histiocytic neoplasms, histiocytic sarcoma is separate from indeterminate cell histiocytosis, a generally benign disorder characterized by proliferation of a CD1a+ and S-100+ population of cells lacking Birbeck granules usually limited to the skin.
  
  
  METHODS
  We present a case of histiocytic sarcoma in a 64-year-old man presenting as a peritonsillar mass and secondarily involving the skin.
  
  
  RESULTS
  The malignant cells in the extracutaneous foci of disease expressed macrophage-associated antigens including S-100 but were CD1a-. The malignant cells in the skin coexpressed CD1a and S-100 but lacked ultrastructural features of Langerhans cells, findings indicative of indeterminate cells.
  
  
  CONCLUSIONS
  We discuss the clinical and histopathologic differential diagnosis in association with prior reported cases of histiocytic sarcoma, particularly in cases involving the skin and cases expressing the Langerhans cell-associated antigen CD1a.
authors.affiliation: Department of Pathology, Saint Louis University School of Medicine, St Louis, MO 63104, USA.
authors.forename: John L
authors.initials: JL
authors.lastname: Frater
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Kling
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Obadiah
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Gardner
authors.forename: Leonard E
authors.initials: LE
authors.lastname: Grosso
authors.forename: Brooke
authors.initials: B
authors.lastname: Resh
authors.forename: M Yadira
authors.initials: MY
authors.lastname: Hurley
mesh_terms: D018949:Antigens, CD1 / Q000378:metabolism*; D000951:Antigens, Neoplasm / Q000378:metabolism; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000378:metabolism; D001761:Bleomycin / Q000008:administration & dosage; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D017024:Chemotherapy, Adjuvant; D003520:Cyclophosphamide / Q000008:administration & dosage; D004317:Doxorubicin / Q000008:administration & dosage; D005047:Etoposide / Q000008:administration & dosage; D006644:Histiocytes / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011241:Prednisone / Q000008:administration & dosage; D012509:Sarcoma / Q000378:metabolism / Q000556:secondary* / Q000628:therapy; D012878:Skin Neoplasms / Q000378:metabolism / Q000556:secondary* / Q000628:therapy; D014067:Tonsillar Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D014750:Vincristine / Q000008:administration & dosage
chemical_list: D018949:Antigens, CD1; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; C419393:CD1a antigen; D001761:Bleomycin; D014750:Vincristine; D005047:Etoposide; D004317:Doxorubicin; D003520:Cyclophosphamide; D011241:Prednisone