Home
HelpTest ID EWS Ewing Sarcoma, by Reverse Transcriptase PCR (RT-PCR)
Useful For
Supporting a diagnosis of Ewing sarcoma and primitive neuroectodermal tumors
Additional Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| SLIRV | Slide Review in MG | No, (Bill Only) | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| EWSF | EWSR1 (22q12), FISH, Ts | Yes | No |
Testing Algorithm
This test is performed in conjunction with SLIRV / Slide Review in MG. Additional testing may be performed after review by pathologist. Upon approval from the requesting clinician, 70012 / Pathology Consultation may be added, if determined to be appropriate.
Special Instructions
Method Name
Reverse Transcriptase Polymerase Chain Reaction (RT-PCR)/Gel
Electrophoresis
(PCR is utilized pursuant to a license agreement with Roche
Molecular Systems, Inc.)
Reporting Name
Ewing Sarcoma, RT-PCRSpecimen Type
VariesA pathology/diagnostic report including a brief history is required.
Specimen Type:
Container/Tube: Surgical Pathology Packaging Kit (Supply T554) requested, but not required
Preferred: Formalin-fixed, paraffin-embedded (FFPE) tissue with a minimum of 5% tumor cell population
Acceptable: Unstained slides with a minimum of 5% tumor cell population; slides may be stained and/or scraped
Collection Instructions:
1. Process all specimens into FFPE blocks prior to submission.
2. If submitting slides, a minimum of ten, 4- to 5-micron thick, unstained slides are required.
Additional Information:
1. A quality specimen is essential for evaluation. Submit only tissue containing tumor cells; minimal tissue is required for evaluation.
2. Special stains performed outside Mayo Medical Laboratories and included with the case may be repeated and charged at the reviewing pathologist's discretion. Testing requested by the referring physician may not be performed if deemed unnecessary by Mayo Clinic pathologist.
Forms: If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
Pathology Test Request Form (T246) (http://www.mayomedicallaboratories.com/it-mmfiles/pathology-request-form.pdf)
Oncology Test Request Form (T729) (http://www.mayomedicallaboratories.com/it-mmfiles/oncology-request-form.pdf)
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Ambient (preferred) | |
| Frozen | ||
| Refrigerated | ||
Clinical Information
Ewing sarcoma (ES) and primitive neuroectodermal tumor (PNET), a closely related tumor, are members of the small round-cell tumor group that also includes rhabdomyosarcoma, synovial sarcoma, lymphoma, Wilms tumor, and desmoplastic small round-cell tumor. ES is the second most common malignant tumor of bone in children and young adults. It is an aggressive osteolytic tumor with a high risk of metastasizing. ES can also present as a soft tissue tumor mass. These tumors are usually bland and undifferentiated with relatively low mitotic indexes, which is misleading in light of the rapid growth commonly observed clinically.
While treatment and prognosis depend on establishing the correct diagnosis, the diagnosis of sarcomas that form the small round-cell tumor group can be very difficult by light microscopic examination alone, especially true when only small-needle biopsy specimens are available for examination. The use of histochemical and immunohistochemical stains (eg, MIC2 [CD99], desmin, myogenin, myoD1, WT1) can assist in establishing the correct diagnosis, but these markers are not entirely specific for ES/PNET. Expertise in soft tissue and bone pathology are often needed.
Studies have shown that some sarcomas have specific recurrent chromosomal translocations. These translocations produce highly specific gene fusions that help define and characterize subtypes of sarcomas that are useful in the diagnosis of these lesions.(1-4)
The balanced t(11;22)(q24;q12) chromosomal translocation produces the EWSR1-FLI1 fusion transcript and is present in 95% of ES and PNET. Because the EWSR1-FLI1 fusion transcript is a common finding in ES/PNET, in soft tissues these 2 lesions are essentially identical. Less common are the t(21;22)(p22;q12) or EWSR1-ERG transcript, present in <5% of ES/PNET tumors, and the t(7:22)(p22;q12) or EWSR1-FEV transcript, present in <1% of these tumors. These fusion transcripts can be detected by reverse-transcriptase PCR (RT-PCR), by FISH, chromogenic in situ hybridization, or by classical cytogenetic analyses. The RT-PCR and FISH procedures are the most sensitive methods to detect these fusion transcripts.(3)
Reference Values
An interpretative report will be provided.
Cautions
Reliable results are dependent on adequate specimen collection and processing. This test has been validated on formalin-fixed, paraffin-embedded tissues; other types of fixatives are discouraged. Improper treatment of tissues, such as decalcification, may cause PCR failure. False-negative results may occur in tumor specimens when tumor cells comprise <5% of the cell population. Tumor cells may be enriched by macrodissection to avoid false-negative results.
Clinical diagnosis and therapy should not be based solely on this assay. The results should be considered in conjunction with clinical information, histologic evaluation, and additional diagnostic tests.
Day(s) Performed
Monday through Friday; Varies
Report Available
8 daysPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.CPT Code Information
81401-EWSR1/FLI1
81401-EWSR1/ERG
88381-Microdissection, manual