Pathology Lab Procedures: Tissue Preparation and Staining

This report provides an overview of histopathology lab procedures, with a focus on the steps involved in preparing tissue samples for microscopic examination. The report details the key stages of tissue preparation, including fixation to preserve cells, grossing which involves careful examination and dissection, processing to prepare samples for automated instruments, embedding in a supporting medium, sectioning using a microtome, and staining to make the specimens visible under a microscope. The report also mentions specific practices at the RMIT pathology lab, such as the use of formaldehyde as a fixative and the thickness of sections cut. Furthermore, it provides examples of specific staining techniques used to diagnose conditions like viral hepatitis and cirrhosis. The document highlights the importance of each step in ensuring accurate diagnosis through microscopic analysis.

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Pathology and lab medicine
Name
Institution
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Introduction
There exist several aims to examine the tissues and cells of human being under the
microscope. Biological and medical research is supported by knowledge of the typical structure
and the role of cells and tissues, organs and structures (1). The cells and other tissue elements are
arranged in recognizable pattern during the normal healthy state. Alteration in structure of the
cell is brought by Different chemicals and physical influences that are reflected at microscopic
level (1). However, several diseases are featured by common structural and chemical
abnormalities which differ from the common state. Sometimes I face difficulties to handle some
tissue like Bone due to its hardiness. There are some difficulties to cut it into small pieces. This
happens if we do not soak the tissue in decalcifying agent enough time. In RMIT pathology lab,
we soak Bone tissue up to 2 days to make soft (2).
Steps of preparing tissue
There are four steps in histopathology lab that are used in preparing tissue. These are
fixation, grossing, processing, embedding and sectioning (1).
Fixation
This is a significant step in preparing samples for microscopic examination. It aims at
preventing decay and preserving cells and tissues in a life-like state (2). This method work by
deactivating the activities of the enzymes, killing the microorganisms and hardening the sample,
on the other hand, maintaining adequate molecular structure to ensure suitable staining methods
to be applied (1). If the fixation is applied immediately after the separation of sample from its
main blood supply, there will be better outcome.

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In addition, in RMIT pathology laboratory, formaldehyde is the main fixative agent
which is used for fixing tissues. Before specimens are processed, they should be fixed by
immersing them in formalin for 6 to 12 hours
Grossing
This is a process which is also termed as cut-up and it involves vigilant examination and
specimen description in regards to dimensions, appearance and the number of pieces. In the case
of larger samples, further dissection should be done in order to come up with representative
pieces from relevant regions (1-2). Just, for example, the several samples can be removed from
the excision margins of a tumour in order to ensure the very tumour has been entirely detached.
If there are small specimens, then all the specimen can be processed. Furthermore, the sampled
specimens will be put into the cassettes and on the other hand, batches will be put into the
processor of tissue ready for processing through the wax.
Processing
This is the process where lots of specimens are prepared for automated instrument called
tissue processors (2). These devices allow the samples to be penetrated with categorization of
different solvents finishing found in the melted paraffin wax.
Embedding
Embedding is the process where tissues are covered with medium like wax, gelatin or
agar. This medium is important in that when it gets solidified, it will offer cover support during
process of sectioning (1).

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Sectioning
This is the process where segments are cut using microtone. The paraffin pieces are
commonly cut at thickness of 3-5 μm. This size makes sure that the one cell thick layers form the
section(2). But in RMIT laboratory, the section is usually cut at 4μ thick.
Staining
This is the process where the sectioned specimens are dyed ready for examination using
microscope (2).
Conclusion
In RMIT pathology lab tissues are not diagnose because it is teaching lab, but some
tissues that are already diagnosed are examined. For example, we stain liver with Trichrome
stain to diagnose viral hepatitis and cirrhosis. Another example is using Hale’s stain to
demonstrate excessive amounts of bile pigment in the liver, which may be found in cases of
hepatic or extrahepatic biliary obstruction

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References
1. Glauert AM, Lewis PR. Biological specimen preparation for transmission electron
microscopy. Princeton University Press; 2014 Jul 14.
2. Kierszenbaum AL, Tres L. Histology and Cell Biology: An Introduction to Pathology E-
Book. Elsevier Health Sciences; 2015 May 4.