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HelpTest ID: PDGF PDGFB (22q13), Dermatofibrosarcoma Protuberans/Giant Cell Fibroblastoma, FISH, Tissue
Useful For
Identifying PDGFB gene rearrangements/amplification
Confirming the diagnosis of dermatofibrosarcoma protuberans (DFSP)/giant cell fibroblastoma
Excluding the diagnosis for 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 does not include a pathology consult. If a pathology consultation is requested, PATHC / Pathology Consultation should be ordered, and the appropriate fluorescence in situ hybridization (FISH) test will be ordered and performed at an additional charge.
This test includes a charge for the probe application, analysis, and professional interpretation of results for one probe set (2 individual FISH probes). 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)
Reporting Name
PDGFB (22q13), FISH, TsSpecimen Type
TissueShipping Instructions
Advise Express Mail or equivalent if not on courier service.
Necessary Information
1. A pathology report is required for testing to be performed. If not provided, appropriate testing and/or interpretation may be compromised or delayed. Acceptable pathology reports include working drafts, preliminary pathology, or surgical pathology reports.
2. The following information must be included in the report provided:
-Patient name
-Block number - must be on all blocks, slides, and paperwork
-Date of collection
-Tissue source
3. 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:
Preferred:
Specimen Type: Tissue block
Collection Instructions:
1. Submit a formalin-fixed, paraffin-embedded tumor tissue block. Blocks prepared with alternative fixation methods will be attempted but are less favorable for successful results
2. Provide fixation method used.
Additional Information:
1. Paraffin-embedded specimens can be from any anatomic location (skin, soft tissue, lymph node, etc).
2. Bone specimens that have been decalcified will be attempted for testing, but the success rate is approximately 50%.
Acceptable:
Specimen Type: Tissue slides
Slides: 1 Hematoxylin and eosin-stained and 2 unstained
Collection Instructions: Submit 2 consecutive unstained, positively charged, unbaked slides with 5 micron-thick sections of the tumor tissue and 1 slide stained with hematoxylin and eosin.
Specimen Minimum Volume
Slides: 1 Hematoxylin and eosin stained and 2 unstained
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Tissue | Ambient (preferred) | |
| Refrigerated | ||
Clinical Information
Dermatofibrosarcoma protuberans is a superficial, low-grade sarcoma genetically characterized by the unbalanced chromosomal translocation t(17;22)(q21.33; q13.1), usually in the form of a supernumerary ring chromosome. The product of this chromosomal translocation is the COL1A1::PDGFB chimeric gene. 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.
Reference Values
An interpretive report will be provided.
Interpretation
PDGFB will be clinically interpreted as positive, negative, or equivocal.
A neoplastic clone is detected when the percent of cells with an abnormality exceeds the normal cutoff for the PDGFB probe set.
A positive result is consistent with rearrangement/amplification of the PDGFB gene. A positive result may support a diagnosis of dermatofibrosarcoma protuberans (DFSP) or giant cell fibroblastoma (GCF). The significance of this finding is dependent on the clinical and pathologic features.
A negative result suggests a PDGFB gene rearrangement/amplification is not present. A negative 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.
Clinical Reference
1. Abbott JJ, Erickson-Johnson M, Wang X, Nascimento AG, Oliveira AM. Gains of COL1A1-PDGFB genomic copies occur in fibrosarcomatous transformation of dermatofibrosarcoma protuberans. Mod Pathol 2006;19(11):1512-1518
2. Labropoulos SV, Fletcher JA, Oliveira AM, Papadopoulos S, Razis ED. Sustained complete remission of metastatic dermatofibrosarcoma protuberans with imatinib mesylate. Anticancer Drugs 2005;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;47(3):260-265
4. WHO Classification of Tumours Editorial Board, eds. Soft Tissue and Bone Tumours, 5th ed. Lyon: IARC Press; 2020. WHO Classification of Tumours, Volume 3.
Day(s) Performed
Monday through Friday
Report Available
7 to 10 daysTest 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.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)
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 |
Forms
If not ordering electronically, complete, print, and send an Oncology Test Request (T729) with the specimen.
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