Test Catalog

Test ID: JAK2P    
JAK2 (9p24.1) Rearrangement, Hematologic Disorders, FISH, Tissue

Useful For Suggests clinical disorders or settings where the test may be helpful

Providing diagnostic information for hematologic malignancies


Aiding in the determination of whether a targeted JAK2 inhibitor could be useful for therapy

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

This test does not include a pathology consult. If a pathology consultation is requested, PATHC / Pathology Consultation should be ordered and the appropriate fluorescence in situ hybridization (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

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The JAK2 gene codes for a protein tyrosine kinase involved in cytokine signaling. Chromosomal translocations involving JAK2 can lead to the formation of chimeric oncoproteins in hematologic malignancies. Rearrangements involving 9p24.1 are rare abnormalities seen in various hematologic diseases and are typically aggressive. Identification of opportunities to apply targeted therapy with JAK2 inhibitors can be helpful for patients with JAK2 rearrangements.

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.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

A positive result is detected when the percent of cells with an abnormality exceeds the normal cutoff for the probe set.


A positive result suggests rearrangement of the JAK2 locus. A negative result suggests no rearrangement of the JAK2 gene region at 9p24.1.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test is not approved by the US Food and Drug Administration, and it is best used as an adjunct to existing clinical and pathologic information.


Fixatives other than formalin (eg, Prefer, Bouin) may not be successful for fluorescence in situ hybridization (FISH) assays, however nonformalin-fixed samples will not be rejected. 


Paraffin-embedded tissues that have been decalcified are generally unsuccessful for FISH analysis. The pathologist reviewing the hematoxylin and eosin-stained slide may find it necessary to cancel testing.

Supportive Data

Fluorescence in situ hybridization (FISH) analysis was performed on 2 paraffin-embedded tissue samples from patients with previously identified 9p24.1 abnormality and 25 noncancerous lymph node control specimens. Rearrangement of JAK2 was identified in 2 samples. The normal controls were used to generate a normal cutoff for this assay.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Chase A, Bryant C, Score J, et al: Ruxolitinib as potential targeted therapy for patients with JAK2 rearrangements. Haematologica. 2013;98(3):404-408

2. Van Roosbroeck K, Cox L, Tousseyn T, et al: JAK2 rearrangements, including the novel SEC31A-JAK2 fusion, are recurrent in classical Hodgkin lymphoma. Blood. 2011;117(15):4056-4064

3. Roberts K, Li Y, Payne-Turner D, et al: Targetable kinase-activating lesions in Ph-like acute lymphoblastic leukemia. N Engl J Med. 2014;371:1005-101

4. Springuel L, Renauld JC, Knoops L: JAK kinase targeting in hematologic malignancies: a sinuous pathway from identification of genetic alteration towards clinical indications. Haematologica. 2015;100:1240-1253

5. Reshmi SC, Harvey RC, Roberts KG, et al: Targetable kinase gene fusions in high-risk B-ALL: A study from the Children's Oncology Group. Blood. 2017;129:3352-3361