American Society for Clinical Pathology (ASCP) Histotechnologist Practice Test

Which fixative is known to leave tissues very soft due to its rapid penetration?

1. Glutaraldehyde

2. Acetic acid

3. Formaldehyde

4. Glyoxal

The correct answer is: Acetic acid

Acetic acid is recognized for its ability to quickly penetrate tissues, which contributes to softer tissue morphology compared to other fixatives. This rapid penetration facilitates the fixation process but can also lead to the extraction of some intracellular components, which may result in a softer, more fragile tissue structure suitable for certain types of microscopic observations, especially cytological preparations. In contrast, glutaraldehyde is a cross-linking fixative that tends to create a more rigid and preserved structure, making tissues firm rather than soft. Formaldehyde similarly provides good structural preservation but doesn't achieve the same level of rapid penetration as acetic acid. Glyoxal is also a fixative, but it has different chemical properties and uses, often producing softer tissues than formaldehyde but still not as pronounced as the effect of acetic acid. The characteristics of acetic acid make it particularly useful for preserving the morphology of certain cell types and for cytological studies, where soft tissue structure is beneficial for cellular detail assessment.