Short formalin fixation and rapid microwave processing do not affect HER2 testing.

ABSTRACT

Correct and consistent results in estrogen and progesterone receptors, HER2 and Ki67 proliferation rate testing are a basic prerequisite for selecting therapy and individualizing prognosis in patients with breast carcinoma. Preanalytic factors, including time from excision to fixation and time and type of fixation, are critical to obtain reproducible and reliable results in these immunohistochemical assays and their relevance has long been stressed. The ASCO-CAP guidelines on HER2 testing indicated that histologic material including both biopsies and surgical specimens must be fixed for at least 6 h in order to obtain reliable results; however, there is a very limited scientific support regarding the setting at 6 h the minimum fixation time. We demonstrate that with a short fixation time (30') and rapid processing with MW technology (69'), it is possible to achieve an adequate and reproducible assessment of HER2 status. We obtained similar results in HER2 evaluation in breast carcinoma biopsies treated with this short protocol and in the corresponding surgical specimens processed routinely with a 24 h formalin fixation time-i.e., within the guidelines interval time.