Biomarker results are only as good as the tissue chosen. In multifocal or heterogeneous tumours, the block sent for immunohistochemistry or sequencing should hold the highest-grade or most representative component, with adequate tumour content.
State in the report which block was tested, its tumour percentage and its grade. The oncologist reading a normal result needs to know whether it came from the area that mattered.
- Select the block with the highest-grade component for predictive biomarker testing.
- Record the block number, tumour percentage and grade in the report.
- Note when a result may not represent other foci.
- Keep a second block available if a discordant result needs checking.
Why it matters
A biomarker result from the wrong focus can be a false negative that changes treatment.
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