histopathology

Question 1

histopathology

Answer 1

study of disease tissue

Question 2

List some of the hazards associated with working in a Histopathology laboratory

Answer 2

Chemical including fixatives
Stains and chemicals
Physical including sharps and radiation
Biological including cross infection.
    - PPE must be worn

Question 3

Explain what a fixative does and list some features of an ideal fixative

Answer 3

A fixative prevents a histological/cytological sample from decaying

Features:

• Will preserve tissue in life like manner
• Will not add artefact material to tissue
• Will not swell or shrink tissue
• Will be safe for user and environment
• Has convenient shelf life and storage
• Is economical

Question 4

What fixative/s can be used for Cytology smears?

Answer 4

Alcohol (ethanol and methanol)

Question 5

List physical agents that can be used to assist in the fixation of tissues

Answer 5

• Microwave radiation
• Heat
• Ultrasound

Question 6

True or false: Autolysis represents the changes to tissue that occur before fixation due to bacterial contamination

Answer 6

true, prevents bacterial decomposition

is the release of lytic enzymes to self digest

Question 7

What type of fixative is Neutral Buffered Formalin classed as?

Answer 7

A formalin (formaldehyde) fixative - universal

Question 8

Why is Formalin Buffered to a neutral pH?

Answer 8

pH is very important because the further a fixative is from the pH of body tissues the more distortion you can get in the tissue at the cellular level

Question 9

Give an example of a Chemical Fixative that belongs to each of the following groups:
Aldehydes
Oxidising Agents
Protein Coagulants
Unknown Mechanism

Answer 9

Aldehydes:
- Formaldehyde
- Glutaraldehyde
Oxidising agents:
- Osmium tetroxide
- Potassium Dichromate
Protein coagulants:
- Ethanol
- Methanol
Uncertain mechanism
- Mercuric Chloride
- Picric acid

Question 10

What is the function of xylene in tissue processing?

Answer 10

It make the paraffin wax soluble so that the sample can be embedded in it and sections of the sample can be cut

Question 11

Why is the histological section cut to approximately 5μm thick?

Answer 11

• Sample needs to be thin enough for light microscopy (about 1 cell layer thick)
• Makes it easier to evaluate tissue and look at its morphology

Question 12

List method/s used for the collection of Cytology samples

Answer 12

Pap Smears
Endoscopy samples
Some FNA (fine needle aspiration) specimens (e.g. lung, liver, pancreas)

Question 13

Compare the advantages and disadvantages of Histopathology with Cytopathology

Answer 13

Cytology:
- Less invasive process - Faster- Cheaper
Histopathology:
- Can observe tissue as a whole instead of individual cells to determine cause of disease - More detailed and easier to diagnose diseases from

Question 14

List some advantages and disadvantages of Cytology

Answer 14

Cytology Advantages:
• Outpatient procedure
• Rapid collection
• Relatively non invasive
• Accurate
• Inexpensive, Low complication rate

Disadvantages:
• Less information than biopsy
• Adequate sampling can be problematic

Question 15

List some advantages and disadvantages of Histopathology

Answer 15

Histopathology Advantage:
• Rapid penetration
• Easy availability and cheap
• Does not over harden the tissue
• Fixes lipids for frozen sections

Disadvantages:
• Irritant to the nose, eyes and mucous membranes
• Formation of precipitate of paraformaldehyde
• Formation of black formalin pigment