title: Fibrocartilaginous mesenchymoma of bone: a single-institution experience with molecular investigations and a review of the literature.
abstract: OBJECTIVE
  Fibrocartilaginous mesenchymoma is a rare intraosseous lesion, with a total of 26 cases described in the literature. This study describes the clinical, radiological and histological features of eight new cases of fibrocartilaginous mesenchymoma collected at a single institution between 1982 and 2016. The presence of GNAS and IDH1/2 mutations and MDM2 amplification was explored to evaluate possible links between fibrocartilaginous mesenchymoma, fibrous dysplasia, de-differentiated chondrosarcoma and low-grade osteosarcoma.
  
  
  RESULTS
  Eight new cases of fibrocartilaginous mesenchymoma of bone identified in our archives, dating from 1982 to 2016, were reviewed. The diagnosis was not performed on the initial biopsy in any of these cases, due mainly to the absence of obvious cartilaginous differentiation. On imaging, the tumour contained cartilaginous calcifications and showed a very strong uptake of contrast medium after injection. Histologically, the tumour was characterized by spindle cell proliferation mimicking a low-grade spindle cell sarcoma, associated with epiphyseal growth-plate-like nodules of cartilage and bone production. Molecularly, no GNAS and IDH1/2 mutations or MDM2 amplification were found in the cases analysed. Only one case recurred 1 year following intralesional resection. None died of disease.
  
  
  CONCLUSIONS
  This very rare bone tumour has a typical radiological and histological pattern and a favourable survival outcome after treatment. Local recurrences can be prevented with complete surgery. Fibrocartilaginous mesenchymoma does not seem to be related genetically to fibrous dysplasia, low-grade osteosarcoma and de-differentiated chondrosarcoma.
authors.affiliation: Department of Pathology, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Gambarotti
authors.affiliation: Department of Pathology, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Righi
authors.affiliation: Department of Pathology, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Daniel
authors.initials: D
authors.lastname: Vanel
authors.affiliation: Department of Pathology, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Cocchi
authors.affiliation: Department of Pathology, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Benini
authors.affiliation: Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Department of Clinical Sciences and Community Health, University of Milan, Endocrinology and Diabetology Unit, Milan, Italy.
authors.forename: Francesca M
authors.identifier: http://orcid.org/0000-0002-4643-3843
authors.initials: FM
authors.lastname: Elli
authors.affiliation: Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Department of Clinical Sciences and Community Health, University of Milan, Endocrinology and Diabetology Unit, Milan, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Mantovani
authors.affiliation: Department of Orthopedics and Orthopedic Oncology, University of Padova, Padova, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Ruggieri
authors.affiliation: Department of Degenerative and Oncologic Spine Surgery, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Boriani
authors.affiliation: Department of Orthopaedic Oncology, Rizzoli Institute, Bologna, Italy.
authors.forename: Davide M
authors.initials: DM
authors.lastname: Donati
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Treviso, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Sbaraglia
authors.affiliation: Department of Pathology, Rizzoli Orthopaedic Institute, Bologna, Italy.|Department of Pathology, Treviso Regional Hospital, Treviso, Italy.
authors.forename: Angelo P
authors.initials: AP
authors.lastname: Dei Tos
authors.affiliation: Department of Pathology, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Piero
authors.initials: P
authors.lastname: Picci
mesh_terms: D000293:Adolescent; D000328:Adult; D001859:Bone Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008637:Mesenchymoma / Q000175:diagnosis / Q000235:genetics / Q000473:pathology*; D055815:Young Adult
keywords: GNAS; MDM2; bone tumours; fibrocartilaginous mesenchymoma