Lab Test

Test Definition Number : 173
Test Definition Name : KIT sequence analysis
Lab Name : OHSU Knight Diagnostics Lab
Lab Test Number of THIS Version : 1178
Lab Test Name : cKIT-GIST with reflex to PDGFR
Status : Active
Expired : No
Updated : 2018-01-28 07:43 EST

General Attributes

Chromosome Band : 4q12
HUGO Gene Name : [KIT] v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog
ICD-Oncology Code
(includes WHO classification diagnoses)
:

Infectious Disease Attributes

Agent Category :
Non-virus Genus and Species :
Virus Family, Genus, and Species :

Lab-specific Attributes

Method : Polymerase Chain Reaction (PCR) - Real Time
Sequencing - Sanger - Bi-directional
Specimen Source
(for clinical patient care these sources must be validated)
: Solid Tissue Paraffin-Embedded Formalin-Fixed
ICD-10 Code :
Use :
Genetics Category : Acquired (somatic)
SNOMED CT :
LOINC :
Comments : Background: Approximately 80% of gastrointestinal stromal tumors (GISTs) have an oncogenic mutation in the gene encoding KIT tyrosine kinase.1 Another 5-7% of GISTs have a mutation in the gene encoding the related kinase PDGFRA (platelet-derived growth factor receptor alpha).1 KIT and PDGFRA mutations are mutually exclusive in GISTs. In both genes, the observed mutations are invariably in-frame and result in expression of a mutant kinase isoform that has constitutive tyrosine kinase activity. Approximately 10-15% of GISTs have no detectable KIT or PDGFRA gene mutation. Screening for kinase mutations in suspected GISTs can be helpful for the following reasons: 1. The presence of a mutation provides molecular confirmation of the diagnosis. 2. Clinical response to treatment withimatinib mesylate (GleevecTM) is predicted by the kinase mutation status, as detailed in the table below. 3. The progression-free survival of patients with KIT exon 9-mutant GIST is significantly longer when they are treated with 800mg/d imatinib as opposed to 400mg/d.2 In contrast, the PFS of patients with KIT exon 11-mutant tumor is not influenced by drug dosage. Methodology: The testing protocol involves the following steps 1. Microscopic examination of the specimen and macrodissection of tumor-rich areas. 2. DNA extraction and purification. 3 .PCR amplification of selected KIT exons, serially in this order: exon 11, 9, 13 & 17. 4. Screening for mutations by one of two methods: direct, bidirectional sequencing, or real-time PCR with high resolution melting curve analysis. DNA sequencing is used to confirm any mutations picked up by melting curve analysis. 5. The estimated sensitivity of these methods is 20% mutant allele. 6. If KIT mutations are not detected, the specimen wil be reflexed to PDGFRA and appropriate testing charges will be incurred. Please see PDGFRA Information Sheet for Methodology.
Specimen Transport Requirements : Paraffin block or 10 unstained sections (4-5 micron) Due to DNA damage, decalcified specimens are not recommended. Package and ship samples at room temperature. Ship via overnight express. Contact Client Services at (855) 535-1522 for shipping kits and instructions.
Samples Available for Proficiency Test Sample Exchange : Yes

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