What is the risk associated with over-fixing tissue specimens?

Over-fixing tissue specimens poses the significant risk of loss of antigenicity and poor staining results. When tissues are exposed to fixatives for an extended period, the proteins and other cellular components within the tissue can undergo molecular changes that affect their structural integrity. This alteration can mask or modify epitopes—specific parts of antigens that antibodies bind to—leading to diminished binding during immunohistochemical staining.

As a result, the staining quality may be compromised, making it difficult or impossible to accurately visualize specific cellular components or proteins. This can hinder diagnosis and research due to inadequate information about the tissue's biological characteristics. Poor staining results can mislead pathologists, impacting patient care and research findings.

In contrast, increased tissue durability, enhancement of color retention, and improved specimen clarity are not outcomes typically associated with over-fixing; instead, these conditions may be more relevant to optimal, correctly-timed fixation protocols. Proper fixation is a balance that aims to preserve tissue morphology while maintaining antigenicity for further investigation and diagnosis.