Desmoplastic Small Round Cell Tumor (DSRCT) by Reverse Transcriptase PCR (RT-PCR), Paraffin
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Supporting the diagnosis of desmoplastic small-round-cell tumor
Additional Tests Lists test(s) that are always performed, at an additional charge, with the initial test(s)
|Test ID||Reporting Name||Available Separately||Always Performed|
|60254||AP Special Studies Review||No||Yes|
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
This test is performed in conjunction with 60254 AP Special Studies Review. Additional testing may be performed after review by pathologist. Upon approval from the requesting clinician, 60254 AP Special Studies Review could be changed to 5439 Surgical Pathology Consultation, if determined to be more appropriate.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Reverse Transcriptase Polymerase Chain Reaction (RT-PCR)/Gel Electrophoresis
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
DSRCT, RT-PCR, Paraffin
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
A pathology/diagnostic report and a brief history are required.
Preferred: Formalin-fixed, paraffin-embedded (FFPE) tissue
Acceptable: Unstained slides; slides may be stained and/or scraped
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.
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, submit a Pathology/Cytology Request Form (Supply T246) with the specimen.
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
A positive result for EWSR1-WT1 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.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
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.
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.
A total of 36 cases that were diagnosed as desmoplastic small-round-cell tumor by soft tissue pathology experts and by immunohistochemical staining were analyzed. These consisted of 4 frozen tissue specimens and 32 paraffin sections. Three of the cases from frozen and paraffin tissue sections were the same cases for direct comparison. All specimens were also analyzed by Southern hybridization using a sequence internal to the primers as a probe. A few specimens were also analyzed by sequencing the PCR products.
The EWSR1-WT1 product was detected in all 4 (100%) fresh tissues and in 30/32 (94.7%) of the paraffin sections. Southern hybridization detected 1 additional case in the paraffin section that was not detected on the ethidium bromide gel. Sequencing of the fresh tissues and paraffin sections confirmed the sequence of the breakpoint of the fusion transcript of EWSR1 exon 7 to WT1 exon 8. Comparable RT-PCR results were obtained for the 3 cases that were analyzed by frozen and paraffin tissues. Analysis of other small-round-cell tumors (alveolar rhabdomyosarcomas, synovial sarcomas, and Ewing sarcomas [n-12]) were all negative for the EWSR1/WT1 fusion transcript.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Barr FG, Chatten J, D'Cruz CM, et al: Molecular assays for chromosomal translocations in the diagnosis of pediatric soft tissue sarcomas. JAMA 1995;273:553-557
2. Gerald WL, Miller HK, Battifora H, et al: Intra-abdominal desmoplastic small round-cell tumor: Report of 19 cases of a distinctive type of high-grade polyphenotypic malignancy affecting young individuals. Am J Surg Pathol 1991;15:499-513
3. Gerald WL, Rosai J, Ladanyi M: Characterization of the genomic breakpoint and chimeric transcripts in the EWS-WT1 gene fusion of demoplastic, small round-cell tumor. Proc Natl Acad Sci USA 1995;92:1028-1032
4. Jin L, Majerus J, Oliveira A, et al: Detection of fusion gene transcripts in fresh-frozen and formalin-fixed paraffin-embedded tissue sections of soft tissue sarcomas after laser capture microdissection and RT-PCR. Diagn Mol Pathol 2003;12:224-230
Method Description Describes how the test is performed and provides a method-specific reference
The paraffin-embedded tissue is deparaffinized, lysed, and digested. RNA is extracted using either the TRIzol kit (Invitrogen) or High Pure FFPE RNA Micro kit (Roche). DNase digestion is performed. RNA is converted to cDNA via reverse transcription (RT); the cDNA is amplified via PCR. Primers specific for the desmoplastic small-round-cell tumor EWSR1-WT1 transcript are used. Controls are run with each specimen to assess possible contamination issues and overall test performance. The PCR products are separated by gel electrophoresis and stained with ethidium bromide. The agarose gel is viewed under ultraviolet light and photographed to document the results. In some cases, the specimen is further analyzed by FISH and sequencing.(Jin L, Majerus J, Oliveira A, et al: Detection of fusion gene transcripts in fresh-frozen and formalin-fixed paraffin-embedded tissue sections of soft tissue sarcomas after laser capture microdissection and RT-PCR. Diagn Mol Pathol 2003;12:224-230)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 8 a.m.–5 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
1 week/7 days
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
81401-EWSR1/WT1 (t(11;22)) (eg, Ewing sarcoma/peripheral neuroectodermal tumor), translocation analysis, qualitative, and quantitative, if performed
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|83365||DSRCT, RT-PCR, Paraffin||In Process|