Folding - Histology

What is Folding in Histology?

Folding in histology refers to the wrinkling or creasing of tissue sections during the preparation of histological slides. This phenomenon can occur at various stages of the tissue processing workflow, including embedding, sectioning, and mounting. The presence of folds can significantly impact the quality of the histological sections, affecting microscopic examination and diagnostic accuracy.

Why Does Folding Occur?

There are several reasons why folding might occur in histological sections. These include:

Improper embedding of the tissue in the paraffin block, leading to uneven surfaces.
Sectioning technique errors, such as incorrect angle or pressure applied during microtomy.
Variations in tissue consistency, where tougher or more fibrous areas fold more easily.
Mounting errors, such as improper placement on the slide or inadequate stretching of the section in the water bath.

How Can Folding Be Prevented?

To minimize the occurrence of folds in histological sections, several best practices can be followed:

Ensure proper embedding with the tissue oriented correctly and fully supported by paraffin.
Use a sharp and well-maintained microtome blade to achieve smooth and even cuts.
Optimize the cutting angle and pressure to match the tissue type.
Use a water bath at the appropriate temperature to float and stretch the sections without causing artifacts.
Carefully transfer sections from the water bath to the slide to avoid creating wrinkles.

What Are the Consequences of Folding?

Folding can have several negative consequences on histological analysis:

It can obscure cellular and structural details, making it challenging to interpret the slide accurately.
Folds can lead to uneven staining, where some areas might be overstained while others are understained.
Diagnostic errors can occur due to misinterpretation of tissue architecture.
It may necessitate the re-cutting and re-staining of sections, leading to delays and increased costs.

How Is Folding Detected?

Folding is typically detected during the examination of histological slides under a microscope. Common signs of folding include:

Visible wrinkles and creases in the tissue section.
Discontinuities or disruptions in the normal tissue architecture.
Irregular staining patterns.

What Are Some Techniques to Correct Folding?

When folding is detected, several corrective measures can be taken:

If folds are detected early during mounting, the section can sometimes be gently stretched or repositioned using fine forceps.
In some cases, re-cutting the tissue block and preparing a new section might be necessary.
Advanced techniques, such as using heated water baths or employing specialized adhesives, can help reduce the incidence of folds.

Are There Any Technological Advances to Reduce Folding?

Recent technological advances have contributed to reducing the occurrence of folding in histological sections:

Automated tissue processors and embedding centers offer more consistent and controlled processing conditions.
Microtomes with advanced features, such as motorized cutting and adjustable angles, provide greater precision.
Innovative slide adhesives and coating techniques improve tissue adherence and reduce movement during mounting.

Conclusion

Folding in histology is a common artifact that can affect the quality and accuracy of tissue examination. By understanding its causes and implementing best practices, the incidence of folds can be minimized, leading to more reliable histological analysis. Ongoing advancements in technology and methodology continue to enhance the ability to produce high-quality histological sections with fewer artifacts.