title: P63 expression as a biomarker discriminating giant cell tumor of bone from other giant cell-rich bone lesions.
abstract: BACKGROUND
  Giant cell tumor of bone (GCTOB) is a locally aggressive neoplasm that accounts for 5% of all primary bone tumors. This tumor overlaps in histopathologic and radiographic presentations with different malignant, benign, and metabolic giant cell-rich lesions. The purpose of this study is to evaluate p63 expression status in giant cell tumor of bone in comparison with other giant cell-rich lesions.
  
  
  METHODS
  In a cross-sectional study we examined immunohistochemical expression of p63 in a series of 100 giant cell-rich bone lesions, including 31 giant cell tumors of bone, 14 osteosarcomas (including 3 giant cell-rich variants), 18 aneurysmal bone cysts (including one solid variant), 8 non-ossifying fibromas, 17 chondroblastomas, 8 tenosynovial giant cell tumors, and 4 brown tumors.
  
  
  RESULTS
  Immunohistochemical analysis showed p63 nuclear expression in 96.8% of giant cell tumors of bone, 14.3% of osteosarcomas, 50% of non-ossifiying fibromas, 22.2% of aneurysmal bone cysts, 68.7% of chondroblastomas, 75.0% of brown tumors and none of the tenosynovial giant cell tumors. Taking into account the intensity of staining, we identified strong staining in 48.4% of giant cell tumors of bone, 35.3% of chondroblastomas and 7.1% of osteosarcomas (in 2 cases which were both giant cell-rich variants). Considering extent of staining, extensive staining was only observed in 58.0% of giant cell tumors of bone, 23.5% of chondroblastomas and 14.3% of osteosarcomas.
  
  
  CONCLUSIONS
  A large number of giant cell tumors of bone (96.8%) are positive for p63, which is considerably more than any other giant cell-rich lesion. However, positive staining for p63 is not specific for GCTOB and may be seen in other lesions such as chondroblastoma, non-ossifying fibroma, brown tumor, and giant cell-rich osteosarcoma. P63 is a sensitive (96.8%) and relatively specific marker for discriminating GCTOB from other types of giant cell-rich lesions. We suggest a combined scoring method for p63 IHC staining interpretation in GC-rich lesions, considering both intensity and extent of reaction, with a 2+ cut off as a more accurate marker for the diagnosis of GCTOB within the appropriate clinical context.
authors.affiliation: Department of Pathology and Laboratory Medicine, Shafa Yahyaean Orthopedics Hospital, Mojahedin Islam Ave., Baharestan Sq., P.O. Box: 1157637131, Tehran, Iran; Department of Pathology, School of Medicine, Iran University of Medical Sciences, Shahid Hemmat Expressway, P.O. Box: 15785-6171, Tehran, Iran. Electronic address: tinashooshtarizadeh@gmail.com.
authors.forename: Tina
authors.initials: T
authors.lastname: Shooshtarizadeh
authors.affiliation: Department of Pathology, School of Medicine, Iran University of Medical Sciences, Shahid Hemmat Expressway, P.O. Box: 15785-6171, Tehran, Iran. Electronic address: mandanarh@yahoo.com.
authors.forename: Mandana
authors.initials: M
authors.lastname: Rahimi
authors.affiliation: Department of Pathology, School of Medicine, Iran University of Medical Sciences, Shahid Hemmat Expressway, P.O. Box: 15785-6171, Tehran, Iran. Electronic address: movahedinia.s@tak.iums.ac.ir.
authors.forename: Sajjadeh
authors.initials: S
authors.lastname: Movahedinia
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D017824:Bone Cysts, Aneurysmal / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D001859:Bone Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D002648:Child; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005260:Female; D018212:Giant Cell Tumor of Bone / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D015726:Giant Cells / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008875:Middle Aged; D012516:Osteosarcoma / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; C081876:CKAP4 protein, human; D008565:Membrane Proteins
keywords: Giant cell tumor of bone; Giant cell-rich lesions; p63 Expression