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HelpTest Code PDGF PDGFB (22q13), Dermatofibrosarcoma Protuberans/Giant Cell Fibroblastoma, FISH, Tissue
Reporting Name
PDGFB (22q13), FISH, TsUseful For
Confirming the diagnosis of dermatofibrosarcoma protuberans (DFSP)/giant cell fibroblastoma (GCF) and excluding other spindle neoplasms that closely simulate the DFSP histology, including dermatofibroma (benign fibrous histiocytoma), neurofibroma, spindle cell lipoma, and a variety of other benign and malignant spindle cell neoplasms
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| _PBCT | Probe, +2 | No, (Bill Only) | No |
| _PADD | Probe, +1 | No, (Bill Only) | No |
| _PB02 | Probe, +2 | No, (Bill Only) | No |
| _PB03 | Probe, +3 | No, (Bill Only) | No |
| _IL25 | Interphases, <25 | No, (Bill Only) | No |
| _I099 | Interphases, 25-99 | No, (Bill Only) | No |
| _I300 | Interphases, >=100 | No, (Bill Only) | No |
Testing Algorithm
This test includes a charge for application of the first probe set (2 FISH probes) and professional interpretation of results.
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Additional charges will be incurred for all reflex probes performed. Analysis charges will be incurred based on the number of cells analyzed per probe set. If no cells are available for analysis, no analysis charges will be incurred.
Appropriate ancillary probes may be performed at consultant discretion to render comprehensive assessment. Any additional probes will have the results included within the final report and will be performed at an additional charge.
Method Name
Fluorescence In Situ Hybridization (FISH)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
TissueNecessary Information
1. A pathology report is required in order for testing to be performed. Acceptable pathology reports include working drafts, preliminary pathology or surgical pathology reports.
2. A reason for testing must be provided. If this information is not provided, an appropriate indication for testing may be entered by Mayo Clinic Laboratories.
Specimen Required
Submit only 1 of the following specimens:
Specimen Type: Tissue
Preferred: Tissue block
Container/Tube: Formalin-fixed, paraffin-embedded tumor tissue block
Collection Instructions: Blocks prepared with alternative fixation methods may be acceptable; provide fixation method used
Acceptable: Slides
Specimen Volume: Four consecutive, unstained, 5 micron-thick sections placed on positively charged slides and 1 hematoxylin and eosin-stained slide
Specimen Minimum Volume
Two consecutive, unstained, 5-micron-thick sections placed on positively charged slides and 1 hematoxylin and eosin-stained slide.
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Tissue | Ambient (preferred) | ||
| Refrigerated | |||
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Reference Values
An interpretive report will be provided.
Day(s) Performed
Monday through Friday
CPT Code Information
88271x2, 88291-DNA probe, each (first probe set), Interpretation and report
88271x2-DNA probe, each; each additional probe set (if appropriate)
88271x1-DNA probe, each; coverage for sets containing 3 probes (if appropriate)
88271x2-DNA probe, each; coverage for sets containing 4 probes (if appropriate)
88271x3-DNA probe, each; coverage for sets containing 5 probes (if appropriate)
88274 w/modifier 52-Interphase in situ hybridization, <25 cells, each probe set (if appropriate)
88274-Interphase in situ hybridization, 25 to 99 cells, each probe set (if appropriate)Â Â Â Â Â Â Â Â
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PDGF | PDGFB (22q13), FISH, Ts | In Process |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 54697 | Result Summary | 50397-9 |
| 54700 | Interpretation | 69965-2 |
| 54699 | Result | 62356-1 |
| CG928 | Reason For Referral | 42349-1 |
| 54919 | Specimen | 31208-2 |
| 54702 | Source | 31208-2 |
| 54703 | Tissue ID | 80398-1 |
| 55130 | Method | 85069-3 |
| 55131 | Additional Information | 48767-8 |
| 53397 | Disclaimer | 62364-5 |
| 54704 | Released By | 19139-5 |
Clinical Information
Dermatofibrosarcoma protuberans (DFSP) is a superficial, low-grade sarcoma genetically characterized by the unbalanced chromosomal translocation t(17;22)(q21;q13), usually in the form of a supernumerary ring chromosome. The product of this chromosomal translocation is the chimeric gene COL1A1-PDGFB. Rearrangements of this gene have been detected in approximately 90% of DFSP and its related infantile form, giant cell fibroblastoma, but not in other tumors.
Interpretation
A neoplastic clone is detected when the percent of cells with an abnormality exceeds the normal reference range for the PDGFB FISH probe.
A positive result is consistent with rearrangement/amplification of the PDGFB gene locus on 22q13 and supports the diagnosis of dermatofibrosarcoma protuberans (DFSP) or giant cell fibroblastoma (GCF). A negative result is consistent with no rearrangement/amplification of the PDGFB gene locus on 22q13. However, this result does not exclude the diagnosis of DFSP or GCF.
The degree of PDGFB copy gain/amplification/rearrangement varies in individual tumors and among different cells in the same tumor. It is not currently known if patients with different levels of rearrangement/amplification have the same prognosis and response to therapy.
Cautions
This test is not approved by the FDA and it is best used as an adjunct to existing clinical and pathologic information.
Fixatives other than formalin (eg Prefer, Bouin) may not be successful for FISH assays, however nonformalin-fixed samples will not be rejected.
Paraffin-embedded tissues that have been decalcified are generally unsuccessful for FISH analysis. The pathologist reviewing the hematoxylin and eosin-stained slide may find it necessary to cancel testing.
Supportive Data
FISH analysis was performed on 49 formalin-fixed paraffin-embedded tissue samples: 24 dermatofibrosarcoma protuberans (DFSP) tumors, 5 giant cell fibroblastoma (GCF) tumors, and 20 non-DFSP/GCF tumors. Normal controls were used to generate a normal cutoff for this assay. Amplification of PDGFB was identified in 20 or 24 (83%) and all 5 GCF tumors. Amplification or rearrangement was not identified in the 20 non-DFSP/GCF tumors.
Clinical Reference
1. 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 Nov;19(11):1512-1518
2. Labropoulos SV, Fletcher JA, Oliveira AM, et al: Sustained complete remission of metastatic dermatofibrosarcoma protuberans with imatinib mesylate. Anticancer Drugs 2005 April;16(4):461-466
3. Macarenco RS, Zamolyi R, Franco MF, et al: Genomic gains of COL1A1-PDGFB occur in the evolution of giant cell fibroblastoma into dermatofibrosarcoma protuberans. Genes Chromosomes Cancer 2008 Mar;47(3):260-265
Method Description
The test is performed using a laboratory-developed PDGFB dual-color break-apart strategy probe (BAP). Formalin-fixed paraffin-embedded tissues are cut at 5 microns and mounted on positively charged glass slides. The selection of tissue and the identification of target areas on the hematoxylin and eosin (H and E)-stained slide is performed by a pathologist. Using the H and E-stained slide as a reference, target areas are etched with a diamond-tipped etcher on the back of the unstained slide to be assayed. The probe set is hybridized to the appropriate target areas and 2 technologists each analyze 50 interphase nuclei (100 total) with the results expressed as the percent of abnormal nuclei.(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[11]:1512-1518)
Report Available
7 to 10 daysSpecimen Retention Time
Slides and H&E used for analysis are retained by the laboratory in accordance to CAP and NYS requirements. Client provided paraffin blocks and extra unstained slides (if provided) will be returned after testing is complete.Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.Forms
If not ordering electronically, complete, print, and send an Oncology Test Request (T729) with the specimen.