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HelpTest ID DSRCT Desmoplastic Small Round-Cell Tumor by Reverse Transcriptase PCR (RT-PCR)
Useful For
Supporting the diagnosis of desmoplastic small round-cell tumor
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 slide review. 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
Desmo Small Round-Cell Tumor,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
Desmoplastic small round-cell tumor (DSRCT) is a member of the small round-cell tumor group that also includes rhabdomyosarcoma, synovial sarcoma, lymphoma, Wilms tumor, and Ewing sarcoma. DSRCT is a type of sarcoma that affects mainly children and adolescent males, usually in the form of widespread intra-abdominal growth not related to any specific organ system. The tumor is composed of angulated nests of small round cells with an abundant desmoplastic stroma. The tumor cells show multiphenotypic differentiation and are usually positive for cytokeratin and desmin.(1-4) These tumors can express renal, epithelial, muscle, and endocrine markers.
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, desmin, cytokeratin, and WT1) can assist in establishing the correct diagnosis, they cannot distinguish between DSRCT and other small round-cell tumors. 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 and are useful in the diagnosis of these lesions.(1-4)
DSRCT is associated with a unique chromosomal translocation t(11:22)(p13;q12) that involves the EWSR1 and the WT1 genes. EWSR1 is the breakpoint site of translocations associated with Ewing sarcoma and WT1 is a gene altered in some Wilms tumors. The translocation results in a fusion of the 2 genes with expression of a chimeric EWSR1-WT1 product. The most common breakpoints involve the intron between EWSR1 exon 7 and 8 and the intron between WT1 exons 7 and 8. Analyses of these transcripts have shown an in-frame fusion of RNA encoding the amino-terminal domain of EWSR1 to the zinc finger of the DNA-binding domain of WT1.
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 or 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/WT1 (t(11;22)) (eg, Ewing sarcoma/peripheral neuroectodermal tumor), translocation analysis, qualitative, and quantitative, if performed
88381-Microdissection, manual