Touch Imprints for Fluorescent In Situ Hybridization Analysis of Well-Differentiated Liposarcoma

Le résumé fourni par la source

Liposarcoma (LS) is the most common type of soft tissue sarcoma studied by cytogenetics. Four types of LS are recognized by the World Health Organization. These subtypes include well-differentiated, dedifferentiated, myxoid/round cell, pleomorphic, and mixed. Well-differentiated LS (WDLS) accounts for approximately half of all malignant lipomatous tumors. Some of these types mimic benign fatty tissue histologically, and WDLSs well-differentiated liposarcomas and lipomas can be very difficult to separate histologically. Molecular changes found in WDLS include chromosome amplification, translocation, ring and giant rod chromosomes. Specific genes thought to be pathogenic in WDLS and dedifferentiated liposarcoma include CDK4 and MDM2. Both are proto-oncogenes involved in cell cycle control. Overexpression can be demonstrated with the use of fluorescent in situ hybridization (FISH) on material obtained using touch imprints at the time of surgery with a fast turnaround time. During gross examination of the surgical specimens, touch imprints were procured. This material was then used for FISH analysis of MDM2 amplification. Results were reported as MDM2/CEP12 signal ratios. Ratios greater than 2:1 were considered positive. Of the 8 cases examined, 4 WDLSs were identified. The remaining 4 cases consisted of 3 lipomas with fat necrosis and 1 localized massive lymphedema specimen. The WDLS cases consistently demonstrated MDM2 overexpression, while the benign specimens did not. MDM2 amplification is a unique genetic finding in WDLSs and can be used to help distinguish these entities. Our study demonstrates that touch imprint material obtained during gross examination is suitable for FISH analysis of MDM2 overexpression and can expedite diagnosis.

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