title: MRI characteristics of lipoma and atypical lipomatous tumor/well-differentiated liposarcoma: retrospective comparison with histology and MDM2 gene amplification.
abstract: OBJECTIVE
  To review the reliability of MR imaging features for the purpose of distinguishing lipoma and atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL).
  
  
  METHODS
  A retrospective review of 87 patients with histologically proven lipomatous tumors was performed. All underwent MR imaging, assessing lipomatous content, septation, and nodules. The associations between these features and tumor diagnosis based on morphology and the presence or absence of MDM2 amplification were explored. The age of the patient and the size and location of the lesion were also recorded for statistical analysis.
  
  
  RESULTS
  Of the 87 patients, 54 were classified as lipomas and 33 as ALT/WDL. MR identified ALT/WDL with a sensitivity of 90.9 % (CI 74.5-97.6) and a specificity of 37.0 % (CI 24.6-51.3). The positive and negative predictive values were 46.9 % (CI 34.5-59.7) and 86.9 % (CI 65.3-96.6), respectively. The mean age of patients with ALT/WDL was greater (60 years [range 40-83 years]) than those with lipoma (52 years [range 10-79 years]) (p = 0.025). The mean size of ALT/WDL (18.7 cm [range 5-36 cm]) was significantly greater than lipoma (13.9 cm [range 3-32 cm]) (p = 0.003). Features that increased the likelihood of ALT/WDL included: patient age over 60 years, maximal lesion dimension over 10 cm, location in lower limb, and presence of non-fatty areas, by a factor of 2.61-6.25 times.
  
  
  CONCLUSIONS
  ALT/WDL and lipoma have overlapping MR imaging characteristics. The most reliable imaging discriminators of ALT/WDL were size of lesion and lipomatous content, but due to the overlap in the MRI appearances of lipoma and ALT/WDL, discrimination should be based on molecular pathology rather than imaging.
authors.affiliation: Department of Radiology, Royal National Orthopaedic Hospital, Stanmore, Middlesex, HA7 4LP, UK.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Brisson
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kashima
authors.forename: David
authors.initials: D
authors.lastname: Delaney
authors.forename: Roberto
authors.initials: R
authors.lastname: Tirabosco
authors.forename: Andrew
authors.initials: A
authors.lastname: Clarke
authors.forename: Suzie
authors.initials: S
authors.lastname: Cro
authors.forename: Adrienne M
authors.initials: AM
authors.lastname: Flanagan
authors.forename: Paul
authors.initials: P
authors.lastname: O'Donnell
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005260:Female; D005784:Gene Amplification; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008067:Lipoma / Q000175:diagnosis* / Q000235:genetics* / Q000473:pathology; D008080:Liposarcoma / Q000175:diagnosis* / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2