title: Immunophenotypic distinction between pigmented villonodular synovitis and haemosiderotic synovitis.
abstract: OBJECTIVE
  Haemosiderotic synovitis (HS) is caused by excessive bleeding into a joint. It occurs secondary to a variety of conditions and needs to be distinguished from pigmented villonodular synovitis (PVNS) for the purposes of treatment. The histopathological distinction between these conditions, particularly in biopsy specimens, can be problematic.
  
  
  METHODS
  Immunophenotypic findings in 20 cases of PVNS and 20 cases of HS were analysed using monoclonal antibodies against proliferation (Ki-67), apoptosis (bcl2), macrophage (CD14, CD68, HLA-DR) and osteoclast (CD51) antigens.
  
  
  RESULTS
  Macrophages in PVNS and HS expressed CD14 and HLA-DR. The giant cells in PVNS, but not those in HS, expressed CD51 and were negative for CD14 and HLA-DR, indicating that these cells had an osteoclast phenotype. Considerably more CD51-expressing mononuclear cells were noted in PVNS compared with HS. The Ki-67 proliferation index was higher in PVNS than in HS.
  
  
  CONCLUSIONS
  The findings indicate that there are immunophenotypic differences in giant cells between PVNS and HS, and that expression of CD51 and a high Ki-67 index effectively distinguishes between these two conditions.
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Nuffield Orthopaedic Centre, UK.
authors.forename: G
authors.initials: G
authors.lastname: Mahendra
authors.forename: K
authors.initials: K
authors.lastname: Kliskey
authors.forename: N A
authors.initials: NA
authors.lastname: Athanasou
mesh_terms: D000293:Adolescent; D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology; D017209:Apoptosis; D015415:Biomarkers / Q000378:metabolism; D049109:Cell Proliferation; D003937:Diagnosis, Differential; D006486:Hemosiderosis / Q000150:complications*; D006801:Humans; D016130:Immunophenotyping; D039564:Integrin alphaV / Q000378:metabolism; D019394:Ki-67 Antigen / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D009130:Muscle, Smooth / Q000378:metabolism / Q000473:pathology; D010010:Osteoclasts / Q000378:metabolism / Q000473:pathology; D013585:Synovitis / Q000175:diagnosis* / Q000209:etiology / Q000276:immunology* / Q000473:pathology; D013586:Synovitis, Pigmented Villonodular / Q000175:diagnosis / Q000276:immunology / Q000473:pathology; D055815:Young Adult
chemical_list: D000911:Antibodies, Monoclonal; D015415:Biomarkers; D039564:Integrin alphaV; D019394:Ki-67 Antigen