KIT Mutations

Specimen Collection, Storage, and Shipping

Test Information:

This assay detects activating mutations in exons 8, 9, 11, 13, 17, and/or 18 of the KIT gene, involved in various neoplasms, including, but not limited to, gastrointestinal stromal tumors (GISTs), mastocytosis, AML, and acral and mucosal melanomas. Specific mutations of KIT may have important clinical implications. For example, in patients with GIST, KIT D816V mutation in exon 17 is associated with imitanib resistance, whereas KIT exon 11 is associated with imatinib sensitivity. Imatinib resistance of KIT exon 9 may be overcome by increased drug doses. The prognostic role of KIT mutation in AML is mixed. KIT mutation in adults CBF-AML is likely associated with increased risk of relapse in adult AML with t(8;21), but not in adult AML with inv(16) or cases of pediatric CBF-AML.

Mutations are detected using PCR followed by dideoxynucleotide sequencing. The sensitivity cut-off is approximately 20% mutated cells.

Requisition Code:

KIT mutations – indicate on requisition which exons (ex 8, ex 9, ex 11, ex 13, ex 17, ex 18, or all) should be tested

CPT Code:

81272; G0452-26 (add G88381 if manual microdissection is needed)

Turn Around Time:

7-10 days

Specimen Requirements:

Fluid

Collect:            Peripheral blood: 2-5 mL in EDTA (purple top) tube

                        Bone marrow: 2-5 mL in ACD (yellow top) or EDTA (purple top) tube

Storage:          Room temperature

Transport:        See Standard Shipping Procedures

Paraffin Block

Decalcified specimens are not accepted.

Collect:            Formalin-fixed, paraffin embedded tissues

Storage:          Room temperature

Remarks:        Submit the paraffin block, 1 H&E with marked location of most abundant tumor (or photocopy of marked H&E) and an approximate % of tumor cells in the area and a copy of the Surgical Pathology report.

Transport:        See Standard Shipping Procedures

References:
  1. Ashida A, et al., Pathological activation of KIT in metastatic tumors of acral and mucosal melanomas. Int J Cancer 2009;124:862–8.
  2. Chen W, et al., Prognostic Significance of KIT Mutations in Core-Binding Factor Acute Myeloid Leukemia: A Systematic Review and Meta-Analysis. PLoS One. 2016 Jan 15;11(1):e0146614.
  3. Künstlinger H, et al., Gastrointestinal stromal tumors with KIT exon 9 mutations: Update on genotype-phenotype correlation and validation of a high-resolution melting assay for mutational testing. Am J Surg Pathol. 2013 Nov;37(11):1648-59.