Pathology Flashcards
What are the most common lab errors?
a) analytical
b) pre-analytical error
c) post-analytical error
b) pre-analytical error
Mislabelling where the specimen and requisition don’t have the same label
Once a specimen arrives to the lab, what is the first step the pathologist takes?
Weight and measure its dimensions
Why do we ink margins?
- For orientation and mapping (proximal to distal)
- You ink all portions that where separated from adjacent tissue, where separation from that plane required a physical act
Positivity of a margin suggests what?
Suggests non-resection, and that local control of the tumour is still needed
Do you paint/ink skin?
No, because it is in contact with air and was not in contact with adjacent tissue.
What is a positive margin?
=Tumour is touching ink
Very low grade tumours, can do a capsular exicision, true or false?
True
High grade Sarcoma, can do a capsular exicision, true or false?
False,
Do a wide-local excision
What is the goal of processing?
To convert a gross specimen into thin cassettes/slides that can examine under a microscope
How thin does a specimen need to be cut into before it can be examined under a microscope?
1 to 2 cells thick.
Need a single optical plane
How big is a cell?
5 microns
5/1000th of a mm
What instrument is used to cut a specimen into smaller slices?
Microtome
Why can’t you cut/linearize a specimen directly with a microtome?
It has water in it, that causes surface tension. The tissue cannot be cut or linearized properly.
What are 2 ways to solidify water?
- Freeze water
- Remove water and replace it with another solid
Tissue processing essentially replaces water with what?
Parrafin wax
Once a tissue is parrafin wax solidified, is it fixed yet?
No
What does a fixative do in fixation?
Tissue is killed
Methylated and cross-linked the proteins (denatured them)
What are examples of fixative?
Formalin
D5
Alcohol
When can you NOT fix a tissue?
When a viable tissue is required for analysis
Ex tissue culture, bacterial culture, gram stain
Does fixation kill DNA?
No
only denatures protein
What is tissue fixation?
Rendering tissue SOLID and invulnerable to autolysis
What is tissue processing?
Rendering tissue solid
solidifying water with paraffin wax, or frozen section
Why don’t we do frozen section on every specimen?
Tissue distorted and contour/shape is lost.
What does “defer to permanent” mean?
Distortion artifact of frozen section is too severe and is interfering with safe/accurate diagnosis.
