title: MR imaging of lipoma and liposarcoma.
abstract: OBJECTIVE
  To evaluate whether lipoma, atypical lipomatous tumors, and liposarcomas can be differentiated by MR images.
  
  
  METHODS
  The MR images of 59 lipomatous lesions and liposarcomas were retrospectively reviewed. Apart from size, surgical site, location and margins, the percentage of fat of the tumor volume was assessed as none, 1-75%, 75-95%, or 95-100%.
  
  
  RESULTS
  None of the 18 liposarcomas contained fat that could be recognized by MR imaging. The 3 atypical lipomatous tumors all contained fat but less than 75% of the tumor volume. In 32 of 38 ordinary lipomas, the percentage of fat was 95-100%, and in 4 less than 95% of the tumor volume. Two lipomas did not contain fat that could be recognized by MR imaging.
  
  
  CONCLUSIONS
  A lesion which predominantly has a fat signal is, in all probability, an ordinary lipoma. Lesions with less fat, but still mostly fatty, may either be lipoma or atypical lipomatous tumor. In this group, the discrimination between these two entities cannot be based upon imaging features. In the absence of a fat signal, liposarcoma or lipoma cannot be differentiated from other soft tissue tumors.
authors.affiliation: Department of Diagnostic Radiology, Karolinska Hospital, Stockholm, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Einarsdottir
authors.forename: V
authors.initials: V
authors.lastname: Söderlund
authors.forename: O
authors.initials: O
authors.lastname: Larson
authors.forename: G
authors.initials: G
authors.lastname: Jenner
authors.forename: H C
authors.initials: HC
authors.lastname: Bauer
mesh_terms: D000273:Adipose Tissue / Q000473:pathology; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008067:Lipoma / Q000175:diagnosis*; D008080:Liposarcoma / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D012189:Retrospective Studies; D012983:Soft Tissue Neoplasms / Q000175:diagnosis*