Most molecular failures start before the sequencer. Fix tissue in 10% neutral buffered formalin promptly, ideally within an hour of removal, for roughly 6 to 72 hours; under- and over-fixation both degrade nucleic acids. Avoid harsh acid decalcification for any sample that may need sequencing — use EDTA instead. When selecting a block, choose the one with the highest tumour content and circle the area for macrodissection, and record the estimated tumour cell percentage on the request.
- Fix in 10% neutral buffered formalin promptly, for about 6 to 72 hours.
- Use EDTA rather than acid decalcification when molecular testing may follow.
- Choose the block with the highest tumour content and mark it for macrodissection.
- Record the estimated tumour cell percentage on the molecular request.
Why it matters
A failed or low-quality assay can delay targeted treatment by weeks.
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