Tissue Processing Steps in Histopathology

Tissue Processing in Histopathology

Steps Involved

1. Fixation: Preserves the tissue, preventing decay and autolysis. Common fixatives include formalin, ethanol, and methanol.
2. Dehydration: Removes water from the tissue using solutions of increasing concentration (e.g., 70%, 95%, and 100% ethanol).
3. Clearing: Replaces ethanol with a solvent (e.g., xylene or toluene) to prepare the tissue for infiltration.
4. Infiltration: Replaces the solvent with melted wax (e.g., paraffin or beeswax).
5. Embedding: Places the tissue in a block of wax, allowing for sectioning.
6. Sectioning: Cuts the tissue into thin slices (typically 4-10 μm) using a microtome.
7. Mounting: Attaches the section to a glass slide.
8. Staining: Enhances visibility of tissue components using dyes (e.g., hematoxylin and eosin).

Factors Affecting Tissue Processing

• Fixative type and duration: Affects tissue morphology and antigenicity.
• Temperature and pH: Influence enzyme activity and tissue degradation.
• Tissue size and type: Impact processing time and section quality.
• Equipment and reagent quality: Affect the reliability of results.

Quality Control Measures

• Tissue handling and storage: Prevents contamination and degradation.
• Reagent quality control: Ensures consistency and effectiveness of processing.
• Equipment maintenance: Prevents instrument failure and ensures optimal performance.
• Section quality control: Verifies section thickness, staining, and morphology.

Tissue Processing in Histopathology

Steps Involved

• Fixation preserves tissue, preventing decay and autolysis, using common fixatives like formalin, ethanol, and methanol.
• Dehydration removes water from tissue using solutions of increasing concentration (e.g., 70%, 95%, and 100% ethanol).
• Clearing replaces ethanol with a solvent (e.g., xylene or toluene) to prepare tissue for infiltration.
• Infiltration replaces the solvent with melted wax (e.g., paraffin or beeswax).
• Embedding places the tissue in a block of wax, allowing for sectioning.
• Sectioning cuts the tissue into thin slices (typically 4-10 μm) using a microtome.
• Mounting attaches the section to a glass slide.
• Staining enhances visibility of tissue components using dyes (e.g., hematoxylin and eosin).

Factors Affecting Tissue Processing

• Fixative type and duration affect tissue morphology and antigenicity.
• Temperature and pH influence enzyme activity and tissue degradation.
• Tissue size and type impact processing time and section quality.
• Equipment and reagent quality affect the reliability of results.

Quality Control Measures

• Tissue handling and storage prevent contamination and degradation.
• Reagent quality control ensures consistency and effectiveness of processing.
• Equipment maintenance prevents instrument failure and ensures optimal performance.
• Section quality control verifies section thickness, staining, and morphology.