Immunohistochemistry and molecular tests can only be as good as the fixation behind them. Delay between excision and formalin, too little formalin, or too short or too long a fixation all degrade antigens and nucleic acids.
For breast specimens, receptor testing standards specify placing tissue in 10% neutral buffered formalin promptly and fixing for between 6 and 72 hours. More generally, a formalin volume about ten times that of the tissue, incision of large specimens to let formalin in, and recording the time of excision and of immersion are established good practice.
- Record the time of excision and the time the specimen entered formalin.
- Use about ten times the tissue volume of 10% neutral buffered formalin.
- Incise or slice large specimens so formalin can penetrate.
- Keep breast specimens for receptor testing within 6 to 72 hours of fixation.
Why it matters
A falsely negative receptor or biomarker result from poor fixation can cost a patient an effective treatment.
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