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FLT3 Gene Mutations

AML, Acute Myeloid Leukemia, Myelodysplastic Syndrome, MDS,FLT3 Internal Tandem Duplication, FLT3 D835, FLT3 ITD, FLT3 Tyrosine Kinase Domain

Test Codes

EPIC: LAB1231590, Abbreviation: GFLT3

Department

Molecular Pathology

Specimen Collection Criteria

Collect (preferred specimen): Bone marrow aspirate in one Lavender-top EDTA. (Minimum: 0.5 mL)

Also acceptable: Blood in one Lavender-top EDTA. (Minimum: 1.0 mL)

Physician Office/Draw Specimen Preparation

Do not centrifuge. Maintain specimen in original collection tube, refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: Blood or bone marrow, refrigerated (2-8°C or 36-46°F) in original collection tube. (Minimum: 1.0 mL blood or 0.5 mL bone marrow)

Rejection Criteria

• Frozen specimens.
• Centrifuged specimens.
• Specimens in clot or SST tubes.
• Specimens not collected and processed as indicated.
• Mislabeled or unlabeled samples.

In-Lab Processing

Do not centrifuge. Maintain specimen in original collection tube, refrigerated (2-8°C or 36-46°F) prior to testing.

Storage

Specimen Stability for Testing:

Room temperature (20-26°C or 68-78.8°F): 48 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F) 7 days.

Extracted DNA may be available for additional testing if clinically indicated. Contact the Molecular Pathology Laboratory for verification.

Laboratory

Royal Oak Molecular Pathology Laboratory

Performed

Twice per week, dependent upon test volume.
Results available in 5 – 7 business days.

Reference Range

Not detected.

Test Methodology

Polymerase Chain Reaction (PCR) followed by Capillary Electrophoresis.

Interpretation

This test detects the two types of mutation in the FLT3 gene, reported in cases of acute myeloid leukemias (AML). The internal tandem duplication (ITD) mutation within the juxtamembrane region of FLT3 and the point mutation at Asp835 within the kinase domain lead to constitutively activated tyrosine kinase activity.

Clinical Utility

The FLT3 gene encodes a cell surface receptor tyrosine kinase that is expressed on early hematopoietic stem cells. Activating mutations in FLT3 occur in a subset of patients with acute myeloid leukemia (AML). The mutation generally occurs as either an internal tandem duplication (FLT3-ITD) within the juxtamembrane domain, or as a missense point mutation within the tyrosine kinase domain (FLT3-TKD) at codon D835.

The FLT3-ITD mutation occurs in approximately 30% of AML cases and is associated with a significantly poorer outcome in normal karyotype AML. In current NCCN guidelines, the presence or absence of a FLT3-ITD mutation, as well as the associated allelic ratio, comprise part of the risk stratification criteria for non-APL AML. Multiple FLT-3 inhibitors, including midostaurin and gilteritinib, are FDA approved and/or NCCN-guideline recommended for use in AML patients with FLT3-ITD.

FLT3-TKD mutations occur in approximately 10% of cases. The prognostic impact of FLT3-TKD mutations remains controversial. However, patients with FLT3-TKD mutations are eligible for treatment with FLT3 inhibitors by current NCCN guidelines.

CPT Codes

81245, 81246, G0452.

Contacts

Last Updated

8/19/2024