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.
Parrafin wax, 2 important properties?
Completely viscous at high temperature
Complete solid at cool temperatures
One full gear turn of the microtome gives what thickness of cut?
5 microns
H&E stain is essentially what?
A fabric dye
Why use H&E stain? i.e. what is histochemistry?
To differentially highlight different elements in a tissue by exploiting their different chemical properties
(i.e. nucleic acids vs protein)
What molecule a radically different charge properties than any other?
DNA
phosphodiester back bone (tons of negative charge)
Cationic dye is what colour? Anionic
Cationic - Blue (DNA)
Anionic - Red (cytoplasm)
What are 4 kinds of special stains?
- Histochemistry
- Immunohistochemistry
- In situ hybridization
- Immunofluoresence
Name a tumor where cytogenics of the tumour is diagnostic?
Lymphoma (Burkitt’s)
8q14
mic oncogene translocated under immunoglobulin promoter
POS may ask about specific translocations associated with certain tumours, true or false?
True
Can a karyotype be done on fixed tissue?
Depends on the kind of fixation
Why did we start using Karyotypes in medicine? (cytogenics)
The application of cytogenics was first applied in obstretics, for diagnosis of Trisomy disorders.
What stage of cell cycle are cells trapped into for cytogenic/karyotype analysis?
Trap them in metaphase
Giemsa uses what chemical property to differentiate between structure?
Redox status
Giemsa is what kind of stain?
A silver-impregnated stain
What is a tissue/tumor of epithelial origin?
Carcinoma
What is a tissue/tumor of mesenchymal origin?
Sarcoma
What is a tissue that is CD45+ve?
S100 +ve?
Lymphoma
Tissue that is S100 +ve?
Melanoma
What tumor has almost all cells in S-phase (i.e. is growing so quickly)? What is the problem with that?
Burkitt’s lymphoma
In S-phase means Tremendous apoptosis –> Tumor lysis
What is a sarcoma of skeletal muscle origin called?
Rhabdomyosarcoma
What is a vascular sarcoma?
Angiosarcoma
List 4 skeletal muscle markers (Histogenesis)
MMMD
- Myogensis
- Myoglobin
- MyoD1
- Desmin
List 2 smooth muscle markers
- Actin
- Smooth Muscle actin
List 2 neural tissue markers
- S100
- PgP9.5
List 4 Vascular markers
- CD31
- Cd34
- Factor VIII
- D240 (lymphatics)
What are 6 ancillary studies one can use?
- Electron microscopy
- FISH
- Conventional Cytogenetics
- Flow cytometry
- Molecular studies
- Microbiology cultures
What is the fixative for electron microscopy?
Glutaraldehyde
What stain do you use/see on a frozen section?
H&E
What is “Tissue Fix”?
Formaldehyde 2-5%
A fixative
Histology vs Cytology?
Histology - see the tissue/cell in its 3D architecture
Cytology - individual aggregated disorganized cells
