Aims: Accurate assessment of HER2 status is essential for selection of patients for HER2-targeted treatment such as trastuzumab. This study investigated the hypothesis that delayed fixation impairs HER2 assessment.
Methods: 9 carcinomas were received fresh, and samples were fixed immediately or put in fixative at time intervals up to 24 h. All carcinomas were scored as 3+ with immunohistochemistry in properly fixed tissue.
Results: 2 of 9 carcinomas (95% CIs 6% to 56%) showed reduced immunohistochemical staining with delays in fixation of 1 and 8 h. One carcinoma showed low-level amplification with fluorescence in situ hybridisation (FISH) when properly fixed and was not amplified after delayed fixation. The other carcinomas were amplified at all time points.
Conclusions: Delayed fixation impaired HER2 protein expression assessed using immunohistochemistry in 22% of 3+ carcinomas. HER2 amplification assessed using FISH may be less affected.
Keywords: Breast; Fixation; Immunohistochemistry; In Situ Hybridisation.
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