PDGFB, 22q13, for Dermatofibrosarcoma Protuberans/Giant Cell Fibroblastoma, FISH
Method Description Describes how the test is performed and provides a method-specific reference
Formalin-fixed, paraffin-embedded tissues are cut at 4 microns and mounted on positively-charged glass slides. Five slides are prepared, with 2 slides stained with hematoxylin and eosin (H and E); the other 3 are left as unstained slides. The selection of tissue and the identification of target areas on an H and E-stained slide is performed by a pathologist. Using the H and E slide as a reference, target areas are etched with a diamond-tipped etcher on the back of the unstained slide to be assayed. Abnormalities involving the PDGFB locus at 22q13 are detected using a break-apart PDGFB FISH probe (Mayo-developed). The break-apart probe design consists of a 3' flanking region of the PDGFB gene labeled in SpectrumGreen (G) and a 5' flanking region labeled in SpectrumOrange (R). The probe set is applied to the appropriate target areas, denatured, and hybridized overnight. Two independent scorers analyze 100 interphase nuclei each (200 total). Normal interphase nuclei show 2 yellow fusion (F) signals caused by juxtaposition of the R and G signals, which indicates genomic integrity of the PDGFB locus on 22q13. Normal patterns also include 1F (up to 30%), 1F+1R (up to 10%), and 1F+1G (up to 10%). Abnormal nuclei will have split of the R and G indicating rearrangement (signal pattern of 1R1G1F), or will have 2F plus multiple red signals, consistent with the presence of the formation of a supernumerary ring chromosome. If the results of the 2 observers are acceptable, the result will be reported out as positive or negative for rearrangement/amplification of the PDGFB locus 22q13 according to the 2005 ISCN nomenclature. The results are interpreted and reported by a working group pathologist.(Abbott JJ, Erickson-Johnson M, Wang X, et al: Gains of COL1A1-PDGFB genomic copies occur in fibrosarcomatous transformation of dermatofibrosarcoma protuberans. Mod Pathol 2006 November;19:1512-1518)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 8 a.m.-4:30 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
1 week/7 days
Performing Laboratory Location The location of the laboratory that performs the test