Translocations and amplifications of chromosome 12 in liposarcoma demonstrated by the LSI CHOP breakapart rearrangement probe.
BACKGROUND
Liposarcomas display a number of molecular abnormalities involving chromosome 12. Myxoid and round cell liposarcomas are characterized by t(12;16)(q13; p11) or t(12;22)(q13;q12) translocations. Amplifications occur within the 12q13-15 region of atypical lipomatous tumors and well-differentiated liposarcomas but not lipomas.


OBJECTIVE
To investigate the performance characteristics of the LSI CHOP Breakapart Rearrangement Probe for the diagnosis of myxoid/round cell liposarcomas and atypical lipomas/well-differentiated liposarcomas.


METHODS
We investigated a series of lipomatous neoplasms (5 lipomas, 5 well-differentiated liposarcomas, 22 myxoid/round cell liposarcomas, 2 liposarcomas not otherwise specified, and 2 dedifferentiated liposarcomas) and normal myometrium for abnormalities in the q13-15 region of chromosome 12. Cases were studied for the presence or absence of t(12;16)(q13;p11) or t(12;22)(q13;q12) translocations by the LSI CHOP Breakapart Rearrangement Probe. These probes contain a sequence encompassing the SAS and CDK4 genes. Four or more copies of this sequence were considered to represent amplification of these genes.


RESULTS
Rearrangement of the CHOP gene was seen in all evaluable myxoid liposarcomas. Rearrangements were seen in 1 dedifferentiated liposarcoma but not in normal myometrium or lipomas. Probe signal amplification was seen in all 5 well-differentiated liposarcomas and 1 myxoid liposarcoma. No signal amplification was seen in lipomas or myometrium.


CONCLUSIONS
Demonstration of translocations t(12; 16)(q13;p11) and t(12;22)(q13;q12) by the LSI CHOP Breakapart Rearrangement Probe appears to correlate with round cell/myxoid liposarcoma. The probe also demonstrated amplification of the 12q13-15 region in well-differentiated liposarcomas, making it useful for the diagnosis of these neoplasms. In a significant percentage of cases, high background fluorescence or poor probe staining made interpretation difficult.
ARUP Laboratories, Salt Lake City, Utah, USA.
Carlynn
C
Willmore-Payne
Joseph
J
Holden
Kristi C
KC
Turner
Alan
A
Proia
Lester J
LJ
Layfield
D002881:Chromosomes, Human, Pair 12 / Q000235:genetics*; D018076:DNA, Complementary; D005784:Gene Amplification; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008080:Liposarcoma / Q000175:diagnosis* / Q000235:genetics*; D011933:Reagent Kits, Diagnostic; D051742:Transcription Factor CHOP / Q000235:genetics*; D014178:Translocation, Genetic
C497249:DDIT3 protein, human; D018076:DNA, Complementary; D011933:Reagent Kits, Diagnostic; D051742:Transcription Factor CHOP