By the end of this section, you will be able to:
- Explain why preserved organs may look different in size and colour between in the body vs. on display
- List the changes a pathologist will look for when examining an organ/tissue
Now that we are ready to look at our specimen, what are we looking for?
How to View Pathology Specimens by Jennifer Kong and Adrian Marcuzzi, licensed under All Rights Reserved
Macroscopic Observation (Gross Specimens)
Remember that we are looking to see how the specimen differs from normal. For gross specimens, the pathologist is looking for changes in:
- Is it larger? Indicating extra growth of either normal tissue or abnormal tissue
- Is it smaller? Indicating cell death or destruction of tissue
- Does it have the proper shape?
- Is it distorted in any way?
- Colour*: (this is best evaluated before fixation)
- Is there a change in colour in parts of the specimen that are unusual? This often happens with infection (white blood cells), tumours where the cells are different, and loss of certain tissues.
- Is the specimen firmer than usual? Indicating perhaps extra fluid or perhaps a tumour or deposits of something that is normally not there
- Is it squishier than usual? Usually a sign of tissue destruction
- Is the structure what we expect?
- Was it formed properly?
- Has it been modified through the disease process?
*Colour: The DHPLC specimens no longer retain their original colour due to fixation, oxidation and bleaching over time.
Remember that tissue is normally clear and so we stain it to be able to distinguish the various parts of the tissue (e.g. H&E stain). The colour and intensity of the stain gives us hints as to the makeup of the cells that form the tissue.
To prepare for your video lesson on histology, we first need a primer on the tissue we are examining: epithelial tissue. Epithelial tissue is made from strongly connected cells, forming a ‘sheet’, covering all the surfaces exposed to the outside world OR lining an organ (outside or inside a hollow organ). Epithelial tissue can be classified based on the shape of the most exposed layer of cells (squamous, columnar, cuboidal, pseudostratified) and whether the sheet is a single layer (simple) or multiple layers (stratified). As skin is the most exposed layer, skin is an epithelial tissue. Epithelial tissue is quite varied, based on their function and location within the body.
For a deeper understanding, consider the following chapter – paying particular attention to their cellular makeup (ie with or without a gland), avascularity and functions of epithelial tissue – as they provide the histological background for many of our video lessons on histology.
To get a hint of what is going wrong in the disease process, a pathologist can look at a block of tissue or whole organ for changes in size, shape, colour, texture, and structure. These changes can suggest underlying problems in cellular changes. Microscopic analysis of tissue is possible using thin slices that are stained to enable visibility of cellular organelles and cytosol.