How Do You Process a Tissue Sample?
Tissue sample processing involves several crucial steps to prepare the sample for microscopic examination. This process ensures the tissue's structural integrity and allows for accurate diagnosis.
The first step involves obtaining a fresh tissue specimen. These specimens come from various sources, depending on the type of biopsy or procedure (e.g., surgical biopsy, needle biopsy). [1]
Key Steps in Tissue Processing
The core steps of tissue processing are outlined below:
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Fixation: This crucial step preserves the tissue's structure and prevents decomposition. The sample is immersed in a fixative, such as formaldehyde solution (formalin), which cross-links proteins and stabilizes cellular components. [1, 2]
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Dehydration: Water is removed from the tissue using a graded series of alcohols, typically starting with low concentrations and gradually increasing to absolute alcohol (100%). [1, 2] This prepares the tissue for infiltration with paraffin wax.
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Clearing: The alcohol is replaced with a solvent miscible with both alcohol and paraffin wax, such as xylene. This removes the alcohol and makes the tissue transparent. [1, 2]
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Wax Infiltration (Impregnation): The tissue is then infiltrated with molten paraffin wax, replacing the clearing agent. This process embeds the tissue in a solid medium for easier sectioning. [1, 2]
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Embedding or Blocking Out: The paraffin-infiltrated tissue is carefully oriented and embedded in a fresh block of paraffin wax. This creates a firm, supportive structure for sectioning. [1, 2] The tissue is often placed in a cassette to hold it securely during processing. [3]
Post-Processing Analysis
Once the tissue sample has been processed, it undergoes sectioning (cutting into thin slices) and staining to enhance visibility of cellular structures under a microscope. [Snippet from StatPearls]. This allows for microscopic analysis and diagnosis. [Snippet from StatPearls]
Example: A Biopsy Procedure
To illustrate, consider a skin biopsy. After obtaining the tissue sample, it's promptly placed in formalin for fixation. Subsequent steps involve dehydration, clearing, wax infiltration, and embedding before it's ready for analysis. Various biopsy types, such as surgical biopsies, needle biopsies (including fine-needle aspiration biopsies), and punch biopsies, all follow a similar processing approach although collection methods vary. [4, 5, 6, 7, 8, 9, 10].
