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Test ID NTRK NTRK Gene Fusion Panel, Tumor

Advisory Information

At least 10% tumor content (% of tumor cell nuclei relative to the total number of cell nuclei in the specimen) is required for this assay. The amount of tumor tissue needed is dependent on a variety of preanalytical factors (eg, cellularity, ischemic time, fixation). In general, the specimen adequacy for this test is approximately a 4 cm(2) area of tumor tissue (can be over multiple slides) or 5,000 total cells.

Necessary Information

Pathology report (final or preliminary if a final report not available) must accompany specimen in order for testing to be performed.

Specimen Required


Specimen Type: Tissue

Container/Tube: Tissue block

Collection Instructions: Submit a formalin-fixed, paraffin-embedded tissue block.



Specimen Type: Tissue

Slides: 1 Stained and 10 unstained

Collection Instructions: Submit 1 slide stained with hematoxylin and eosin and 10 unstained, nonbaked slides with 5 micron-thick sections of the tumor tissue.

Secondary ID


Useful For

Identifying solid tumors that may respond to targeted therapies by simultaneously assessing for rearrangements involving the NTRK1, NTRK2, and NTRK3 genes resulting in fusion transcripts


This test is not useful for hematologic malignancies.

Genetics Test Information

This test uses next-generation sequencing to identify rearrangements (fusions) involving the NTRK1, NTRK2, and NTRK3 genes.


The assay was designed to detect the most common NTRK gene fusions and novel gene fusion partners in the targeted gene regions. See NTRK RNA Targeted Gene Fusions table in Special Instructions for details.


Of note, this test is performed to evaluate rearrangements (fusions) within solid tumor samples. This test is not intended for use for hematological malignancies.


This test evaluates formalin-fixed, paraffin-embedded tumor or cytology slides from patients with advanced solid tumors for rearrangements (fusions) involving the NTRK1, NTRK2, and NTRK3 genes to identify candidates for targeted therapy. Current data suggests that solid tumors with NTRK rearrangements may be sensitive to multikinase inhibitors.

Additional Tests

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

Testing Algorithm

When this test is ordered, slide review will always be performed at an additional charge.

Special Instructions

Method Name

Polymerase Chain Reaction (PCR)-Based Next-Generation Sequencing (NGS)

Reporting Name

NTRK Gene Fusion Panel

Specimen Type


Specimen Minimum Volume

Tissue: Entire block
Slides: 1 stained with hematoxylin and eosin and 1 or more unstained nonbaked slides with at least 5,000 total nucleated cells and at least 20% tumor cells

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.

Clinical Information

Targeted cancer therapies are defined as antibody or small molecule drugs that block the growth and spread of cancer by interfering with specific cell molecules involved in tumor growth and progression. Multiple targeted therapies have been approved by the FDA for treatment of specific cancers. Molecular genetic profiling is often needed to identify targets amenable to targeted therapies and to minimize treatment costs and therapy-associated risks.


Fusions involving the NTRK1, NTRK2, or NTRK3 genes (ie, NTRK gene fusions) form through intra- and interchromosomal rearrangements. NTRK gene fusions lead to activation of downstream MAPK, PIK, and STAT3 signaling pathways and act as oncogenic drivers of multiple types of pediatric and adult solid tumors. In solid tumors, the presence of an NTRK gene fusion is a biomarker for response to tropomyosin receptor kinase (TRK) inhibitor therapy.


This test assesses for fusions involving the NTRK1, NTRK2, and NTRK3 genes. The results of this test can be useful in guiding treatment of individuals with advanced solid tumors.


See the NTRK RNA Targeted Gene Fusions table in Special Instructions for details regarding the targeted gene regions evaluated by this test.

Reference Values

An interpretive report will be provided.


An interpretive report will be provided.


This test is not designed to differentiate between somatic and germline alterations. Additional testing may be necessary to clarify the significance of results if there is a potential hereditary risk.


A negative (wild-type) result does not rule out the presence of a rearrangement (fusion) that may be present but below the limits of detection of this assay. The analytical sensitivity of this assay is a minimum coverage of 10 targeted fusion reads with 5 unique fusion molecules in a sample with 10% or greater tumor content.


Only gene rearrangements (fusions) involving targeted breakpoints in NTRK1, NTRK2, and NTRK3 genes will be detected. This test does not detect point mutations, insertion/deletion mutations, large single or multiexon deletions or duplications, or genomic copy number variants in any of the genes tested.


Rare polymorphisms may be present that could lead to false-negative or false-positive results. Test results should be interpreted in the context of clinical findings, tumor sampling, and other laboratory data. If results obtained do not match other clinical or laboratory findings, contact the laboratory for updated interpretation. Misinterpretation of results may occur if the information provided is inaccurate or incomplete.


Reliable results are dependent on adequate specimen collection and processing. This test has been validated on cytology slides and formalin-fixed, paraffin-embedded tissues; other types of fixatives are discouraged. Improper treatment of tissues, such as decalcification, may cause PCR failure.

Clinical Reference

1. Drilon A, Laetsch TW, Kummar S: Efficacy of Larotrectinib in TRK Fusion-Positive Cancers in Adults and Children. N Engl J Med 2018 Feb 22;378(8):731-739 doi: 10.1056/NEJMoa1714448

2. Cocco E, Scaltriti M, Drilon A: NTRK fusion-positive cancers and TRK inhibitor therapy. Nat Rev Clin Oncol 2018 Dec;15(12):731-747 doi: 10.1038/s41571-018-0113-0

Day(s) and Time(s) Performed

Monday through Friday; Varies

Analytic Time

14 days

Performing Laboratory

Mayo Clinic 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 (NTRK3/ETV6 fusion if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
NTRK NTRK Gene Fusion Panel In Process


Result ID Test Result Name Result LOINC Value
606761 Result Summary 50397-9
606762 Result In Process
606763 Interpretation 69047-9
606764 Additional Information 48767-8
606765 Specimen 31208-2
606766 Source 31208-2
606767 Tissue ID 80398-1
606768 Released By 18771-6

NY State Approved