title: Chromosome 12 long arm rearrangement covering MDM2 and RASAL1 is associated with aggressive craniofacial juvenile ossifying fibroma and extracranial psammomatoid fibro-osseous lesions.
abstract: To evaluate the diagnostic value of MDM2 status in craniofacial fibro-osseous lesions, we investigated MDM2 expression by immunohistochemistry and analyzed MDM2 amplification by qPCR in 30 cases of ossifying fibroma (including 13 cases of the juvenile variant) and 17 cases of fibrous dysplasia. Two cases of uncommon extragnathic psammomatoid fibrous dysplasia and a mixed control group of 15 cases of low-grade osteosarcoma and 15 cases of well-differentiated/dedifferentiated liposarcoma were included. MDM2 amplification was found in 33% of ossifying fibromas (peak of 69% for the juvenile variant) and in 12% of fibrous dysplasia, in none of which was MDM2 overexpressed. All control cases exhibited MDM2 amplification and overexpression. To investigate possible polysomy of chromosome 12, we studied RASAL1 amplification, a gene telomeric to MDM2 on the long arm of chromosome 12. RASAL1 amplification was reported in all benign fibro-osseous lesions exhibiting MDM2 amplification but not in controls. Simultaneous amplification of these two genes was significantly higher in juvenile ossifying fibromas compared with fibrous dysplasia (P=0.004), non-juvenile ossifying fibromas (P=0.001), and all other benign craniofacial fibro-osseous lesions combined (P=0.0001). Of the nine cases of juvenile ossifying fibroma exhibiting amplification, three were locally invasive and four were recurrent, suggesting aggressive disease. The two cases of extragnathic psammomatoid fibrous dysplasia also showed MDM2 and RASAL1 amplification with no MDM2 overexpression. This large chromosome 12 rearrangement, spanning MDM2 and RASAL1, is the first recurrent molecular abnormality to be reported in juvenile ossifying fibroma. It may represent both a molecular diagnostic marker and a characteristic of more aggressive forms with a higher risk of recurrence. Finally, the presence of this rearrangement in extragnathic psammomatoid fibro-osseous lesions mimicking ossifying fibromas might reflect a common molecular pathway in their pathogenesis and calls into question the classification of such lesions within fibrous dysplasia.
authors.affiliation: 1] Department of Pathology, University Hospital of Tours and University François Rabelais, Tours, France [2] Laboratory of Biochemistry and Molecular Biology, University Hospital of Tours and University François Rabelais, Tours, France.
authors.forename: Flore
authors.initials: F
authors.lastname: Tabareau-Delalande
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, University Hospital of Tours and University François Rabelais, Tours, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Collin
authors.affiliation: Department of Pathology, Rangueil University Hospital, Toulouse, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Gomez-Brouchet
authors.affiliation: Department of Pathology, La Timone University Hospital, Marseille, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Bouvier
authors.affiliation: Department of Pathology, Léon Bérard Center, Lyon, France.
authors.forename: Anne-Valérie
authors.initials: AV
authors.lastname: Decouvelaere
authors.affiliation: Department of Pathology, University Hospital of Tours and University François Rabelais, Tours, France.
authors.forename: Anne
authors.initials: A
authors.lastname: de Muret
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, University Hospital of Tours and University François Rabelais, Tours, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Pagès
authors.affiliation: 1] Department of Pathology, University Hospital of Tours and University François Rabelais, Tours, France [2] INSERM, UMR 957, Laboratory for Bone Resorption Physiopathology and Primary Bone Tumour Therapy, Faculty of Medicine, University of Nantes, Nantes, France.
authors.forename: Gonzague
authors.initials: G
authors.lastname: de Pinieux
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000175:diagnosis / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics*; D005147:Facial Bones; D005260:Female; D018214:Fibroma, Ossifying / Q000175:diagnosis / Q000235:genetics*; D005357:Fibrous Dysplasia of Bone / Q000175:diagnosis / Q000235:genetics*; D020690:GTPase-Activating Proteins / Q000235:genetics*; D015321:Gene Rearrangement; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics*; D012189:Retrospective Studies; D012886:Skull; D012888:Skull Neoplasms / Q000175:diagnosis / Q000235:genetics; D055815:Young Adult
chemical_list: D020690:GTPase-Activating Proteins; C580923:RASAL1 protein, human; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2