title: Intraosseous atypical chondroid tumor or chondrosarcoma grade 1 in patients with multiple osteochondromas.
abstract: BACKGROUND
  The autosomal dominant condition multiple osteochondromas, formerly called multiple hereditary exostoses, is associated with a risk of malignant progression of osteochondroma into secondary peripheral chondrosarcoma. Most patients with multiple osteochondromas have exostosin-1 or exostosin-2 gene mutations. To our knowledge, it has not been previously reported that patients may also harbor intraosseous (central) chondroid neoplasms, enchondromas, or atypical chondroid tumors or central chondrosarcomas. The combination of osteochondroma and enchondromas also exists in patients with metachondromatosis, a disorder associated with a protein tyrosine phosphatase non-receptor type 11 gene mutation. This study aims to establish any correlation between multiple osteochondromas and intraosseous cartilaginous neoplasms.
  
  
  METHODS
  We retrospectively reviewed all histologically proven intraosseous atypical chondroid tumors or chondrosarcomas in our prospective nationwide Dutch tertiary referral multiple osteochondromas database. Demographic, clinical, radiographic, histological, and genetic data were recorded. The institutional medical ethics review board approved the study.
  
  
  RESULTS
  From 195 adult patients, seven (3.6%) were identified with intraosseous atypical chondroid tumor or chondrosarcoma World Health Organization grade 1 and had a mean age of forty-two years; five of these patients were male. In all cases, radiographic and genetic findings were consistent with multiple osteochondromas, not metachondromatosis; three patients had an exostosin-1 mutation, four patients had an exostosin-2 mutation, and no patients had a protein tyrosine phosphatase, non-receptor type 11 mutation. Six patients underwent successful operative treatment without complications or recurrences after a mean follow-up duration of forty-eight months (range, twelve to 144 months). One patient was scheduled for surgery after biopsy and histologic confirmation. Of the seven patients, five (71%) also developed a peripheral chondrosarcoma in a known osteochondroma during the study period.
  
  
  CONCLUSIONS
  Apart from osteochondromas or peripheral chondrosarcomas, multiple osteochondromas are also associated with intraosseous chondroid neoplasms, potentially resulting in central chondrosarcoma. Therefore, intraosseous lesions should not automatically be regarded as innocuous in this patient population.
authors.affiliation: Department of Orthopedic Surgery, Diakonessenhuis, Utrecht, P.O. Box 80250, 3508 TG Utrecht, the Netherlands. E-mail address: annemariegoud@hotmail.com.
authors.forename: Annemarie L
authors.initials: AL
authors.lastname: Goud
authors.affiliation: Department of Medical Genetics, University and University Hospital of Antwerp, Wilrijkstraat 10, 2650 Edegem, Antwerpen, Belgium. E-mail address: wim.wuyts@uaantwerpen.be.
authors.forename: Wim
authors.initials: W
authors.lastname: Wuyts
authors.affiliation: Department of Orthopedic Surgery, Erasmus MC, University Medical Center, PO Box 2040, 3000 CA Rotterdam, the Netherlands. E-mail address: j.bessems@erasmusmc.nl.
authors.forename: Johannes
authors.initials: J
authors.lastname: Bessems
authors.affiliation: Department of Orthopedic Surgery, Academic Medical Center, PO Box 22660, 1100 DD Amsterdam, the Netherlands. E-mail address: j.a.bramer@amc.uva.nl.
authors.forename: Jos
authors.initials: J
authors.lastname: Bramer
authors.affiliation: Departments of Orthopedic Surgery (J.H.) and Radiology (H.J.v.d.W.), Onze Lieve Vrouwe Gasthuis, Wilrijkstraat 10, 2650 Edegem Antwerpen, PO Box 95500, 1090 HM, Amsterdam, the Netherlands. E-mail address for H.J. van der Woude: h.j.vanderwoude@olvg.nl. E-mail address for J. Ham: s.j.ham@olvg.nl.
authors.forename: Henk Jan
authors.initials: HJ
authors.lastname: van der Woude
authors.affiliation: Departments of Orthopedic Surgery (J.H.) and Radiology (H.J.v.d.W.), Onze Lieve Vrouwe Gasthuis, Wilrijkstraat 10, 2650 Edegem Antwerpen, PO Box 95500, 1090 HM, Amsterdam, the Netherlands. E-mail address for H.J. van der Woude: h.j.vanderwoude@olvg.nl. E-mail address for J. Ham: s.j.ham@olvg.nl.
authors.forename: John
authors.initials: J
authors.lastname: Ham
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002812:Chondroma / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D002813:Chondrosarcoma / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D016208:Databases, Factual; D005097:Exostoses, Multiple Hereditary / Q000150:complications / Q000175:diagnosis* / Q000235:genetics / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D055815:Young Adult