title: Loss of heterozygosity and microsatellite instability are rare in sporadic dedifferentiated liposarcoma: a study of 43 well-characterized cases.
abstract: BACKGROUND
  Defects in mismatch repair proteins have been identified in Lynch syndrome-associated liposarcomas, as well as in rare sporadic sarcomas. However, it is unclear if mismatch repair defects have a role in sarcoma tumorigenesis. Microsatellite instability is a surrogate marker of mismatch repair defects.
  
  
  OBJECTIVE
  To determine whether sporadic dedifferentiated liposarcomas display microsatellite instability and, if so, to evaluate whether such instability differs between the lipogenic and nonlipogenic components of these tumors.
  
  
  METHODS
  The diagnoses of conventional dedifferentiated liposarcoma were confirmed by a combination of morphologic, immunophenotypic, and molecular studies. Standard fluorescence-based polymerase chain reaction, including 5 mononucleotide microsatellite markers (BAT25, BAT26, NR21, NR24, and MONO27), as well as 2 pentanucleotide repeat markers (Penta C and Penta D), was used to test for instability and loss of heterozygosity.
  
  
  RESULTS
  We demonstrated only a single case (1 of 43) with microsatellite instability at one mononucleotide marker. No sarcomas showed high-level microsatellite instability. However, loss of heterozygosity at the pentanucleotide markers was observed in 8 of 43 cases. The presence of loss of heterozygosity was overrepresented in the nonlipogenic (dedifferentiated) components compared with the paired lipogenic (well differentiated) components.
  
  
  CONCLUSIONS
  Mismatch repair defects do not contribute to sporadic dedifferentiated liposarcoma tumorigenesis. Whether the observed loss of heterozygosity drives tumorigenesis in liposarcoma, for example by affecting tumor suppressor or cell cycle regulator genes, remains to be determined.
authors.affiliation: From the Department of Pathology, University of California, San Francisco.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Davis
authors.forename: James P
authors.initials: JP
authors.lastname: Grenert
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Horvai
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics; D054337:Cell Dedifferentiation / Q000235:genetics; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics / Q000473:pathology; D053843:DNA Mismatch Repair / Q000235:genetics; D006801:Humans; D008080:Liposarcoma / Q000235:genetics* / Q000473:pathology*; D019656:Loss of Heterozygosity; D008297:Male; D053842:Microsatellite Instability; D018895:Microsatellite Repeats; D008875:Middle Aged
chemical_list: D014408:Biomarkers, Tumor