Comprehensive panel boosts GIST diagnosis sensitivity  


Test in Focus

Multiple genetic mutations are now known to cause gastrointestinal stromal tumors, or GIST. In this "Test in Focus" episode of the "Answers From the Lab" podcast, Rondell Graham, M.B.B.S., describes Mayo Clinic Laboratories' comprehensive MayoComplete GIST Panel, which covers these mutations for improved diagnosis and treatment.

"This expanded panel is more sensitive for the diagnosis of GIST. It covers not only the most commonly mutated genes but also the less commonly mutated genes and GIST mutations that pursue an aggressive disease course," Dr. Graham says.

The next generation sequencing assay can be used to confirm a diagnosis of GIST in patients who have unusual lesions in the GI tract. For patients already diagnosed with GIST, the assay can pinpoint genetic mutations that inform treatment and prognosis.

"This is a very complete GIST panel," Dr. Graham says. "It is part of a thoughtfully curated menu of tests that focus on all the genes surrounding a specific indication — such as GIST — and also standalone gene tests."

Listen to learn more about Mayo Clinic Laboratories' comprehensive MayoComplete GIST Panel.

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Testing

Useful information

  • Diagnosis and management of patients with gastrointestinal stromal tumors
  • Assessment of microsatellite instability

Specimen requirements

This assay requires at least 20% tumor nuclei

  • Preferred amount of tumor area with sufficient percent tumor nuclei: tissue 216mm(2)
  • Minimum amount of tumor area: tissue 36mm(2)
  • These amounts are cumulative over up to 10 unstained slides and must have adequate percent tumor nuclei
  • Tissue fixation: 10% neutral buffered formalin, not decalcified

For specimen preparation guidance, see Tissue Requirement for Solid Tumor Next-Generation Sequencing. In this document, the sizes are given as 4mm x 4mm x 10 slides as preferred: approximate/equivalent to 144 mm(2) and the minimum as 3mm x 1mm x 10 slides: approximate/equivalent to 36mm(2).

Preferred:

  • Specimen Type: Tissue block
  • Collection Instructions: Submit a formalin-fixed, paraffin-embedded tissue block with acceptable amount of tumor tissue

Acceptable:

  • Specimen Type: Tissue slide
  • Slides: 1 Stained and 10 unstained
  • Collection Instructions: Submit 1 slide stained with hematoxylin and eosin and 10 unstained, nonbaked slides wit 5-micron thick sections of the tumor tissue

Note: The total amount of required tumor nuclei can be obtained by scraping up to 10 slides from the same block

Additional Information: Unused unstained slides will not be returned

  • Specimen Type: Cytology slide (direct smears or ThinPrep)
  • Slides: 1 to 3 Slides
  • Collection Instructions: Submit 1 to 3 slides stained and cover slipped with a preferred total of 5000 nucleated cells, or a minimum of at least 3000 nucleated cells

Note: Glass coverslips are preferred; plastic coverslips are acceptable but will result in longer turnaround times

Additional Information: Cytology slides will not be returned

Performance information

Analytic time: 12 days

Days performed: Monday through Friday

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Barbara J. Toman (@barbaratoman)

Barbara J. Toman

Barbara J. Toman is a Senior Communications Specialist at Mayo Clinic Laboratories. She is also the science writer for Mayo’s Neurosciences Update newsletter, which helps referring physicians to stay informed about Mayo’s treatment and research. Barbara has worked at Mayo Clinic since 2007. She enjoys international travel and cooking.