Practical 3: H&E and Oil Red O Stain Flashcards
What is embedding
The process by which tissues are solidified in a wax mould to create the wax block for cutting thin sections using a microtome
Why do we use paraffin wax for moulds
It provides a supporting media to enable subsequent sectioning of tissue
What does FFPE stand for
Formalin fixed paraffin embedded tissue
What is cryotomy
The use of a refrigerated microtome to cut frozen sections of tissue
When is cryotomy used
(5)
Lipid staining
Rapid H&E for urgent diagnosis
DNA and/or preservation for molecular analysis by PCR
Special investigations - direct immunofluorescence, enzyme histochemistry, immunohistochemistry
Biobanking - storage for research
Why is cryotomy used in lipid staining
Lipids are dissolved out of tissue if they are exposed to the solvents used in paraffin-processing, therefore lipid staining is always performed on frozen tissues
What is the most common lipid stain?
Oil Red O
What is Oil Red O
A red hydrophobic dye which stains all triglycerides and neutral lipids intensely red
When might you need an Oil Red O stain
Disease cases whereby lipids accumulate e.g. liver disease, muscle wasting or lipid storage diseases
Give another stain for lipids other than Oil Red O
Sudan Black B
What is the different between Oil Red O and Sudan Black B
Sudan Black B stains both hydrophobic and phospholipids black
When might H&E be used with cryotomy?
Patient may be having surgery -> need rapid diagnosis of a legion
Excision margin clearance to ensure diseases tissue fully resected
Lymph node clearance in radical surgery - head and neck surgery, radical hysterectomy, axillary clearance for breast cancer
What is the microtome and how is it used (3)
A mechanical device which advances a tissue block by a small thickness over a blade, which then slices off the section
This is then floated onto water to flatten and expand the section
The section is then collected onto a labeled slide
Slides of 10-20 microns are used for what?
Neurohistology
Lipid staining
Slides of 3-5 microns are used for what
Routine light microscope
