Which common fixative is used in histopathology?

Formalin is widely recognized as the most common fixative used in histopathology due to its effectiveness in preserving tissue morphology and cellular detail. It is a solution of formaldehyde in water, most often buffered to a neutral pH and composed of 10% formalin, which is roughly 4% formaldehyde. This fixation process helps to cross-link proteins, stabilizing the tissue architecture and preventing autolysis and putrefaction.

The advantages of formalin include its ability to penetrate tissues relatively quickly, making it efficient for routine tissue processing. It also allows for the preservation of nucleic acids, which is beneficial for various downstream analyses such as molecular diagnostics. Furthermore, formalin fixation is compatible with many subsequent staining techniques, including hematoxylin and eosin staining, which is foundational in pathological evaluation.

In contrast, while ethanol is a commonly used fixative, particularly for cytology specimens, it is not as effective as formalin for preserving morphological details in tissue samples. Acetone, while also employed in particular contexts, is less commonly used for histological specimens due to its rapid dehydration effects, which can lead to shrinkage and distortion of tissues. Mercuric chloride, although effective, has largely fallen out of favor