ER, PR and HER2 results are validated on tissue placed in 10% neutral buffered formalin within an hour of removal and fixed for between six and 72 hours. Under-fixation, common with small core biopsies processed the same day, and long cold ischaemia can both produce false-negative results.
Record the time of removal, the time into formalin and the fixation duration on every breast specimen, and flag deviations in the report so a negative result can be interpreted.
- Place breast tissue in formalin within one hour of removal.
- Fix for at least six and no more than 72 hours before processing.
- Record cold ischaemia and fixation times on the request and in the report.
- Flag out-of-range fixation when reporting a negative ER or HER2 result.
Why it matters
A false-negative receptor result can deny a patient endocrine or HER2-targeted therapy.
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