title: Giant cell tumors: inquiry into immunohistochemical expression of CD117 (c-Kit), microphthalmia transcription factor, tartrate-resistant acid phosphatase, and HAM-56.
abstract: BACKGROUND
  Osteoclast-like giant cells (GCs) in giant cell tumors (GCTs) are thought to derive from a monocyte-macrophage lineage. Microphthalmia transcription factor (MITF) is necessary for osteoclast gene expression and tartrate-resistant acid phosphatase (TRAP) activation; c-Kit plays a role in regulation of MITF.
  
  
  OBJECTIVE
  To gain insight into the differentiation of GCTs of bone (GCTBs) and GCTs tendon sheath (GCTTSs) by investigating immunohistochemical staining for c-Kit, MITF, TRAP, and HAM-56 in the GCs and stroma.
  
  
  METHODS
  Immunoreactivity for CD117 (c-Kit), MITF, TRAP, and HAM-56 was studied in 35 GCTBs, 15 GCTTSs, and 5 foreign-body GC controls.
  
  
  RESULTS
  Across tumors, MITF and TRAP but not c-Kit were generally expressed in GCs; TRAP was variably expressed in stromal cells. The MITF was expressed more consistently in stromal cells of GCTTSs than GCTBs (P < .001). The GCTBs showed more intense MITF stromal (P < .001) and TRAP GC staining (P = .04) than GCTTSs. HAM-56 staining by stromal cells was associated with MITF stromal staining (r2 = 0.6, P < .001).
  
  
  CONCLUSIONS
  Results suggest that MITF and TRAP are expressed during osteoclast differentiation and that a proportion of mononuclear cells in GCTs express the macrophage marker HAM-56. Both GCTBs and GCTTSs show similar patterns of immunohistochemical expression.
authors.affiliation: Department of Pathology, Pennsylvania Hospital, Philadelphia 19107, USA.
authors.forename: Rolando Y
authors.initials: RY
authors.lastname: Ramos
authors.forename: Helen M
authors.initials: HM
authors.lastname: Haupt
authors.forename: Peter A
authors.initials: PA
authors.lastname: Kanetsky
authors.forename: Rakesh
authors.initials: R
authors.lastname: Donthineni-Rao
authors.forename: Carmen
authors.initials: C
authors.lastname: Arenas-Elliott
authors.forename: Richard D
authors.initials: RD
authors.lastname: Lackman
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Martin
mesh_terms: D000135:Acid Phosphatase / Q000276:immunology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001859:Bone Neoplasms / Q000737:chemistry*; D003238:Connective Tissue / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000276:immunology*; D005260:Female; D005870:Giant Cell Tumors / Q000737:chemistry*; D006801:Humans; D007527:Isoenzymes / Q000276:immunology*; D008297:Male; D051739:Microphthalmia-Associated Transcription Factor; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000737:chemistry; D010010:Osteoclasts / Q000737:chemistry; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000502:physiology; D012983:Soft Tissue Neoplasms / Q000737:chemistry*; D000071681:Tartrate-Resistant Acid Phosphatase; D013710:Tendons / Q000737:chemistry; D014157:Transcription Factors / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D004268:DNA-Binding Proteins; C096893:HAM-56 antibody; D007527:Isoenzymes; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; D014157:Transcription Factors; D019009:Proto-Oncogene Proteins c-kit; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase