title: Cytologic and immunocytochemical characterization of feline progressive histiocytosis.
abstract: BACKGROUND
  Feline Progressive Histiocytosis (FPH) is a cutaneous dendritic cell neoplasm characterized by slow progression and spread to internal organs in the terminal stage. FPH is often misdiagnosed as an inflammatory reaction and has not been fully characterized from a cytologic diagnostic perspective.
  
  
  OBJECTIVE
  The purpose of the study was to characterize the cytologic and immunocytochemical aspects useful for FPH diagnosis.
  
  
  METHODS
  Fine-needle aspiration cytologic samples of 5 cases of FPH confirmed by skin biopsy and necropsy were evaluated. Immunocytochemistry with antibodies recognizing CD1a, CD1c, CD3, CD11b, CD18, CD21, and MHCII was performed on air-dried, acetone-fixed smears. E-cadherin expression was assessed on paraffin-embedded skin biopsies. Transmission electron microscopy (TEM) was performed in one case.
  
  
  RESULTS
  Main cytologic findings on variably cellular samples were characterized by single to cohesive large, round to polygonal cells with intermediate to low N/C ratio, abundant clear homogeneous cytoplasm, and round to oval nuclei with rare bi- to multinucleated atypical cells, associated with low numbers of small lymphocytes and/or neutrophils. Neoplastic cells expressed CD1a, CD1c, CD11b, CD18, and MHCII. Anti-CD3 antibodies identified reactive T cells admixed with the neoplastic cells. E-cadherin expression was observed in all but one case. TEM failed to identify Birbeck granules in one case.
  
  
  CONCLUSIONS
  FPH is a distinctive neoplastic lesion composed of nonphagocytizing histiocytes variably admixed with neutrophils and small mature lymphocytes. Immunocytochemical analysis with CD1 is mandatory to confirm a dendritic cell origin. Immunocytochemistry and cytomorphology allowed the specific and rapid diagnosis of FPH on cytologic samples.
authors.affiliation: Department of Veterinary Sciences and Public Health, University of Milan, Milan, Italy.
authors.forename: Nazaré
authors.initials: N
authors.lastname: Pinto da Cunha
authors.forename: Gabriele
authors.initials: G
authors.lastname: Ghisleni
authors.forename: Fabia
authors.initials: F
authors.lastname: Scarampella
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Fabbrini
authors.forename: Monica
authors.initials: M
authors.lastname: Sforna
authors.forename: Luisa
authors.initials: L
authors.lastname: Cornegliani
authors.forename: Mario
authors.initials: M
authors.lastname: Caniatti
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Avallone
authors.forename: Peter
authors.initials: P
authors.lastname: Moore
authors.forename: Paola
authors.initials: P
authors.lastname: Roccabianca
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D018949:Antigens, CD1 / Q000276:immunology*; D044963:Biopsy, Fine-Needle / Q000662:veterinary; D002371:Cat Diseases / Q000175:diagnosis* / Q000473:pathology; D002415:Cats; D005260:Female; D015620:Histiocytic Disorders, Malignant / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D007150:Immunohistochemistry / Q000662:veterinary; D016130:Immunophenotyping / Q000662:veterinary; D008297:Male; D046529:Microscopy, Electron, Transmission / Q000662:veterinary; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D018949:Antigens, CD1
keywords: CD1; Cats; histiocytic disorders; immunocytochemistry; skin