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Test ID: EWSF Ewing Sarcoma (EWS), 22q12 (EWSR1) Rearrangement, FISH, Tissue

Useful For

Supporting the diagnosis of Ewing sarcoma (EWS)/primitive neuroectodermal tumor (PNET), myxoid chondrosarcoma, desmoplastic small, round cell tumor, clear cell sarcoma, and myxoid liposarcoma when used in conjunction with an anatomic pathology consultation


An aid in the diagnosis of EWS when reverse transcriptase-PCR results are equivocal or do not support the clinical picture

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 FISH test will be ordered and performed at an additional charge.


This test includes a charge for application of the first probe set (2 FISH probes) and professional interpretation of results. Additional charges will be incurred for all reflex probes performed. 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.


See the Method Description for specific details.

Method Name

Fluorescence In Situ Hybridization (FISH)

Reporting Name

EWSR1 (22q12), FISH, Ts

Specimen Type


Shipping Instructions

Advise Express Mail or equivalent if not on courier service.

Necessary Information

1. A pathology report is required in order for testing to be performed. Acceptable pathology reports include working drafts, preliminary pathology or surgical pathology reports.

2. 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:


Specimen Type: Tissue

Preferred: Tissue block

Collection Instructions: Submit a formalin-fixed, paraffin-embedded (FFPE) tumor tissue block. Blocks prepared with alternative fixation methods may be acceptable; provide fixation method used.


Acceptable: Slides

Collection Instructions: Four consecutive, unstained, 5 micron-thick sections placed on positively charged slides, and 1 hematoxylin and eosin-stained slide.

Specimen Minimum Volume

Two consecutive, unstained, 5 micron-thick sections placed on positively charged slides and 1 hematoxylin and eosin-stained slide

Specimen Stability Information

Specimen Type Temperature Time Special Container
Tissue Ambient (preferred)

Clinical Information

Ewing sarcoma (EWS)/primitive neuroectodermal tumors (PNET) are members of the small, round cell group of tumors that are thought to originate in cells of primitive neuroectodermal origin with variable degrees of differentiation. The small, round cell group of tumors also includes rhabdomyosarcomas, desmoplastic small, round cell tumors, and poorly differentiated synovial sarcomas. Although immunohistochemical markers can be helpful in the correct diagnosis of these tumors, recent molecular studies have shown the specificity of molecular markers in differentiating specific subtypes of small, round blue-cell tumors. Accurate diagnosis of each tumor type is important for appropriate clinical management of patients.


Ewing tumors are characterized cytogenetically by rearrangements of the EWSR1 gene at 22q12 with FLI1 at 11q24 (t[11;22]) or ERG at 21q22 (t[21;22]) in 85% and 5% to 10% of Ewing tumors, respectively. Less than 1% of cases may have other fusion partners such as ETV1 at 7p22, E1AF at 17q12, or FEV at 2q33. Detection of these transcripts by reverse transcriptase-PCR (RT-PCR) (EWS, Ewing Sarcoma RT-PCR) that allows specific identification of the t(11;22) and the t(21;22), has greatly facilitated the diagnosis of Ewing tumors. However, if the quality of the available RNA is poor, the results are equivocal, or if a rare translocation partner is present, FISH testing has proven to be useful in identifying the 22q12 EWS gene rearrangement in these tumors.

Reference Values

An interpretive report will be provided.


A neoplastic clone is detected when the percent of cells with an abnormality exceeds the normal cutoff for the EWSR1 FISH probe set.


A positive result is consistent with a diagnosis of Ewing sarcoma (EWS)/primitive neuroectodermal tumors (PNET).


A negative result suggests that a EWSR1 rearrangement is not present but does not exclude the diagnosis of EWS/PNET.

Clinical Reference

1. World Health Organization Classification of Tumors. Pathology and Genetics Tumours of Soft Tissue and Bone. Edited by CDM Fletcher, KK Unni, F Mertens: IARC Press; Lyon 2002, pp 298-300

2. Burchill SA: Ewing's sarcoma: diagnostic, prognostic, and therapeutic implications of molecular abnormalities. J Clin Pathol 2003 February;56(2):96-102

3. Riley RD, Burchill SA, Abrams KR, et al: A systematic review of molecular and biological markers in tumors of the Ewing's sarcoma family. Eur J Cancer 2003 January;39:19-30

4. Romeo S, Dei Tos AP: Soft tissue tumors associated with EWSR1 translocation. Virchows Arch. 2010 Feb;456(2):219-34

Day(s) and Time(s) Performed

Samples processed Monday through Sunday.

Results reported Monday through Friday 8 a.m. to 5 p.m.

Analytic Time

7 days

Test Classification

This test was developed using an analyte specific reagent. Its performance characteristics were 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

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)     

88275 – Interphase in situ hybridization, 100 to 300 cells, each probe set (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
EWSF EWSR1 (22q12), FISH, Ts 93806-8


Result ID Test Result Name Result LOINC Value
52187 Result Summary 50397-9
52189 Interpretation 69965-2
54589 Result 62356-1
CG749 Reason for Referral 42349-1
52190 Specimen 31208-2
52191 Source 31208-2
52192 Tissue ID 80398-1
52193 Method 49549-9
55030 Additional Information 48767-8
53827 Disclaimer 62364-5
52194 Released By 18771-6
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