Main Points:

• Freshly harvested tissue of interest should be immediately fixed to avoid degradation.
• 10% Neutral Buffered Formalin (NBF) or 4% Paraformaldehyde solution (PFA) are commonly used for histology. These are effective fixatives for H&E, and the majority of immunohistochemistry (IHC) markers and special stains.
• Optimal fixation is key to best histopathology results.

Broadly, there are two strategies that can be employed to provide this support:

1. We can freeze the tissue and keep it frozen while we cut our sections. These sections are called “frozen sections”.
2. Alternatively, we can infiltrate our tissue specimen with a liquid agent that can subsequently be converted into a solid that has appropriate physical properties, which will allow thin sections to be cut from it. Paraffin wax is such an agent. This produces so-called “paraffin sections”.