The influence of fixation procedure, embedding medium and section thickness on morphometric data in thyroid gland

Area of Science:

• Histology and Cell Biology
• Stereology and Quantitative Morphology
• Endocrinology and Thyroid Research

Background:

• Stereological analysis of thyroid tissue relies on accurate preservation of tissue structure.
• Fixation and embedding procedures can introduce significant artifacts, including tissue shrinkage and deformation.
• Understanding these effects is critical for reliable quantitative assessments of thyroid morphology.

Purpose of the Study:

• To evaluate the impact of different fixation procedures, embedding media, and section thicknesses on stereological measurements of the normal thyroid gland.
• To determine optimal methods for minimizing artifacts and ensuring accurate quantitative analysis of thyroid tissue.

Main Methods:

• Comparison of fixation techniques including Bouin's fixative and glutaraldehyde with and without osmium post-fixation.
• Evaluation of embedding media: paraplast and Epon.
• Analysis of section thickness effects on stereological parameters.
• Assessment of tissue shrinkage and axial deformation using stereological principles.

Main Results:

• A single, centrally located section per thyroid lobe is sufficient for stereological analysis.
• Glutaraldehyde-Epon fixation/embedding resulted in less shrinkage than Bouin-paraplast, though not statistically significant.
• Osmium post-fixation reduced glutaraldehyde-induced shrinkage and sectioning deformation.
• Bouin's fixative with paraplast embedding caused significant interstitial tissue shrinkage; glutaraldehyde-Epon showed less shrinkage.

Conclusions:

• Optimal fixation and embedding are essential for accurate thyroid stereology.
• Glutaraldehyde and osmium fixation with Epon embedding minimize tissue artifacts, allowing for reliable spherical assumptions for follicles and colloids.
• Careful selection of histological preparation methods is paramount for valid quantitative thyroid research.