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Test Code DSRCT Desmoplastic Small Round-Cell Tumor by Reverse Transcriptase PCR (RT-PCR)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Supporting the diagnosis of desmoplastic small round-cell tumor

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, PATHC / Pathology Consultation may be added, if determined to be appropriate.

Special Instructions

Method Name

Reverse Transcriptase Polymerase Chain Reaction (RT-PCR)/Gel Electrophoresis

Reporting Name

Desmo Small Round-Cell Tumor,RT-PCR

Specimen Type


Advisory Information

Special stains performed outside Mayo Clinic 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.

Necessary Information

A pathology/diagnostic report including a brief history is required.

Specimen Required

A quality specimen is essential for evaluation. Submit only tissue containing tumor cells; minimal tissue is required for evaluation.


Supplies: Surgical Pathology Packaging Kit (T554) requested, but not required



Specimen Type: Formalin-fixed, paraffin-embedded (FFPE) tissue with a minimum of 5% tumor cell population

Collection Instructions: Process all specimens into FFPE tissue blocks prior to submission.



Specimen Type: Unstained slides with a minimum of 5% tumor cell population; slides may be stained and/or scraped

Slides: A minimum of ten, 4- to 5-micron thick, unstained slides are required.

Specimen Stability Information

Specimen Type Temperature Time
Varies Ambient (preferred)

Reject Due To








Specimens that have been decalcified (all methods)

Specimens that have not been formalin-fixed, paraffin-embedded

Bone marrow in EDTA

Reference Values

An interpretative report will be provided.


A positive EWSR1-WT1 result is consistent with a diagnosis of desmoplastic small round-cell tumor (DSRCT).


Sarcomas other than DSRCT, and carcinomas, melanomas, and lymphomas are negative for the fusion products.


A negative result does not rule out a diagnosis of DSRCT.

Day(s) and Time(s) Performed

Monday through Friday; Varies

Analytic Time

8 days

Specimen Retention Time

Unused portions of blocks will be returned. Unused slides are stored indefinitely.

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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
DSRCT Desmo Small Round-Cell Tumor,RT-PCR In Process


Result ID Test Result Name Result LOINC Value
54754 Result Summary 50397-9
54755 Result In Process
54756 Interpretation 69047-9
54757 Additional Information 48767-8
54758 Reason for Referral 42349-1
54759 Specimen 31208-2
54760 Source 31208-2
54761 Tissue ID 80398-1
54762 Released By 18771-6

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
EWSF EWSR1 (22q12), FISH, Ts Yes No

Additional Tests

Test ID Reporting Name Available Separately Always Performed
SLIRV Slide Review in MG No, (Bill Only) Yes


1. Pathology/Cytology Information (T707) in Special Instructions

2. If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Pathology Test Request (T246)

-Oncology Test Request (T729)