ASCP Histotechnologist Exam 2025 – 400 Free Practice Questions to Pass the Exam

Formalin fixation is crucial for preserving tissue morphology and ensuring accurate immunohistochemical (IHC) staining, particularly for HER2 testing in breast carcinoma tissues. The recommendation for a minimum of 4 hours and a maximum of 48 hours is based on studies that show adequate fixation time allows for optimal antigen retrieval and better staining outcomes.

Fixation for at least 4 hours ensures that the formalin adequately penetrates the tissue, providing sufficient preservation of cellular structures and molecular components required for accurate HER2 expression analysis. Moreover, a fixation time extending to a maximum of 48 hours allows for variability in tissue density and size, accommodating different specimen types while still achieving reliable results.

Longer fixation durations beyond 48 hours may start to alter tissue antigenicity, diminishing the quality of immunostaining results. Thus, the specified timeframe optimally balances thorough fixation with the preservation of antigen integrity for HER2 testing, ensuring that the procedure yields reproducible and clinically significant results.