title: Differential diagnosis of benign peripheral lipoma from well-differentiated liposarcoma on MR imaging: is comparison of margins and internal characteristics useful?
abstract: OBJECTIVE
  Our objective was to evaluate the reliability of MR imaging in distinguishing between benign lipoma and well-differentiated liposarcoma.
  
  
  METHODS
  The MR images of 35 pathologically proven benign lipomas in 35 patients and 23 well-differentiated liposarcomas in 17 patients were retrospectively reviewed. T1-, T2-, and fat-suppressed T1-weighted images were obtained after administration of gadopentetate dimeglumine. Margins and internal characteristics revealed on the MR images and the degree of contrast enhancement of septa were evaluated. These MR imaging findings were compared for well-differentiated liposarcomas and benign lipomas.
  
  
  RESULTS
  Completely irregular margins were recognized only in benign lipomas with a pathologic diagnosis of infiltrating lipoma. All tumors without a recognizable nonadipose component were benign lipomas (p < 0.05). As for the well-differentiated liposarcomas, thick septa and nodular or patchy nonadipose components were present more frequently in deep and retroperitoneal lesions than in subcutaneous lesions (p < 0.01). No cases showed only thin septa in the deep lesions of well-differentiated liposarcoma, and all cases showed thick septa or nodular or patchy nonadipose components. The septa in well-differentiated liposarcomas enhanced more strongly than did those in benign lipomas. The septa showed no enhancement relative to muscle in 11 of 19 benign lipomas, whereas the septa showed moderate or marked enhancement in all well-differentiated liposarcomas (p < 0.01).
  
  
  CONCLUSIONS
  Careful assessment of margins and internal characteristics on MR imaging can be a useful aid in further distinguishing between biologically different benign lipoma and well-differentiated liposarcoma.
authors.affiliation: Department of Radiology, University of Occupational and Environmental Health, Iseigaoka 1-1, Yahatanisi-ku, Kitakyushu-shi 807-8555, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ohguri
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Aoki
authors.forename: Masanori
authors.initials: M
authors.lastname: Hisaoka
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Watanabe
authors.forename: Katsumi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashimoto
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Nakamura
authors.forename: Hajime
authors.initials: H
authors.lastname: Nakata
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008067:Lipoma / Q000473:pathology*; D008080:Liposarcoma / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009372:Neoplasms, Connective Tissue / Q000473:pathology*; D015203:Reproducibility of Results; D012186:Retroperitoneal Neoplasms / Q000473:pathology*; D012189:Retrospective Studies; D040521:Subcutaneous Tissue / Q000473:pathology