Test Overview
Test Methodology

Polymerase Chain Reaction (PCR) followed by sequencing analysis.

Test Usage

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. Most GISTs characteristically express the KIT receptor tyrosine kinase, and approximately 80% harbor oncogenic mutations within the KIT gene. These primarily involve KIT exon 11, but may also occur in exons 9, 13, and 17. All mutations result in the constitutive activation of KIT, which has led to the use of tyrosine kinase inhibitor drugs (imatinib) as a common therapy for GIST patients. Testing for KIT mutation can aid in the diagnosis of GIST, particularly for tumors that lack KIT expression by immunohistochemistry. Mutation testing may also aid in determining prognosis, and may help predict response to imatinib therapy, both of which have been associated with specific KIT mutations. This DNA sequencing test will detect mutations within exons 9, 11, 13, and 17 of the KIT gene. The tested exons correspond to KIT amino acids 497-513 (exon 9), 550-591 (exon 11), 628-661 (exon 13), and 799-823 (exon 17). Appropriate specimens include formalin fixed paraffin embedded tissue blocks and fresh/frozen tissues. Specimens should contain an adequate proportion of tumor nuclei (>40%) to enable mutation detection.

Reference Range *

Interpretive report provided.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

A negative result does not rule out the presence of a rare KIT mutation outside of the sequenced regions or a low level mutation below the sensitivity of detection (20% mutant allele). Specimens should contain an adequate proportion of neoplastic cells (>40%) to enable mutation detection.

Test Details
Days Set Up
Monday - Thursday
Analytic Time

3 - 10 days

Soft Order Code
GISTS
MiChart Code
KIT Mutation - Exons 9, 11, 13, 17
Synonyms
  • MLABEL
  • GISTS
  • GIST
  • KIT Mutation Detection - GIST
  • KIT Mutation Detection for Gastrointestinal Stromal Tumor
  • KIT Mutation Detection for Imatinib Therapy
  • c-KIT Mutation
  • KIT Exon 9, 11, 13, 17 Mutations
  • KIT Mutation for GIST
Laboratory
Molecular Diagnostics
Section
Molecular Diagnostics
Specimen Requirements
Collection Instructions

For formalin-fixed, paraffin-embedded tissue, a block containing an area with a high percentage of neoplastic cells (for micro-/macro-dissection) is preferred. Unstained, UNBAKED slides (5-8, 10-micron slides; 10-15 if few neoplastic cells are present) with associated H&E stained slide are also acceptable. Decalcified tissue or other fixatives will be accepted and the assay attempted, however these may result in failed testing due to degraded nucleic acid. Both blocks and slides should be stored at room temperature. Store at room temperature.

Normal Volume
Formalin-fixed, paraffin-embedded tissue; Diff-Quik stained aspirate smear. Extracted DNA is also acceptable if extracted in a CLIA certified laboratory.
Additional Information

By ordering this test the clinician acknowledges that informed consent has been obtained from the patient as required by applicable state or federal laws and the ordering clinician has authorization from the patient permitting MLabs to report the test results to the ordering clinician. Test includes microdissection billed as a separate additional charge. Test includes pathologist interpretation of results billed as a separate additional charge. This test is not available without interpretation.

Billing
CPT Code
81272, 88381-TC
Fee Code
NA057, NA037
Pro Fee CPT
G0452-26, 88381-26
Pro Fee Code
81404
Prior Authorization
The Prior Authorization form is required for this test. Click here to download the PDF.
Resources