E-module: Histopathology

Question 1

What does a histopathologist do?

Answer 1

Deals with tissues

Examine sections, noting architecture of tissues, asks what it tells us about a particular condition

Question 2

What does a cytopathologist do?

Answer 2

Deals with cells
Often responsible for taking cells from patients, preparing for examination and then delivering expert diagnosis on cell sample

Question 3

What tissue samples might a histopathologist work with?

Answer 3

Biopsies
Resection specimens
Frozen sections
Post motte season

Question 4

What are biopsies?

Answer 4

Small sections of tissues removed from patient and placed in formalin solution.

Question 5

What is the purpose of formalin solution?

Answer 5

To preserve tissues by cross-linking proteins

Question 6

Why are biopsies embedded in paraffin wax?

Answer 6

To allow very thin sections (2-3um thick) to be cut instrutments known as microtome

Question 7

What sort of questions can microscopic examination of a biopsy tell us?

Answer 7

• is tissue normal?
• is tissue inflamed and if so what is cause?
• is the tissue cancerous and if so what type of cancer?

Question 8

What are biopsies primarily used for?

Answer 8

To make diagnoses e.g. is there a need for surgery

Question 9

Where are resection specimens taken from?

Answer 9

Tissue that has been removed as part of a surgical procedure - they can be processed as for a biopsy

Question 10

What are resections primarily used for?

Answer 10

To look at the stage of a disease

Question 11

What else can be done with tissue from resection specimens?

Answer 11

can also be donated to biobanks and used to inform genomic studies of the disease process, with the input of other medical professionals such as immunologists and microbiologists.

Question 12

When are frozen sections taken?

Answer 12

During surgical procedures

Question 13

What happens to make frozen tissue?

Answer 13

Freshly taken tissue is frozen by a machine known as a cryostat, cut then mounted on glass slides and stained as for biopsies

Question 14

What can frozen tissue do?

Answer 14

Provide a rapid diagnosis in minutes which can be relayed back to surgeon to inform surgery e.g.

• is tissue cancerous
• has all cancerous tissue been removed
• is there another pathological process going on

Question 15

What timescales are involved between a histopathology lab and clinicians?

Answer 15

Frozen section - 30 mins
Biopsies - 2 to 3 days
Resection specimen - 5 to 7 days

Question 16

How can cells be collected for analysis?

Answer 16

• fine needle - can be used to get into a lesion and suck out (aspirate) the cells which can then be analysed

Question 17

What is an advantage of fine needle aspirarates?

Answer 17

It is a powerful technique as needle can penetrate relatively inaccessible tissues e.g. thyroid nodule
- assess suspect mass w/o need for surgery

Question 18

What is the downside of fine needle aspirarates?

Answer 18

Cytopathologist is only looking at cells and unable to comment upon likely architecture of tissue

Question 19

Give an example of how histopathology and cytopathology can be combined and work together.

Answer 19

Kaposi’s sarcoma (a relatively rare cancer) has a skin biopsy which shows spindly looking cells penetrating collagen fibres and an antibody recognising the endothelial cell marker CD31 (typical of endothelial cells) which allows us to define this biopsy as an endothelial cell tumour.
If these biopsies are combined w/fine needle aspirate taken from enlarged lymph nodes then a diagnosis of reactive lymphadenopathy can be given due to the mixed cell population observed.

Question 20

What can high levels of circulating antibodies recognising double stranded DNA be associated with?

Answer 20

Systemic lupus erythematosus (SLE)
Sjögren’s syndrome
Rheumatoid arthritis

Question 21

How can antibodies be manufactured to be used to detect specific molecules in immunohistochemistry?

Answer 21

Attachments are added to the Fc region of the antibody (a.k.a conjugations)

Question 22

What sort of attachments can be added to manufactured antibodies?

Answer 22

• enzymes e.g. peroxidase, alkaline phosphate w/ colourless substrate to give coloured product
• fluorescent probes allow rapid measurement of molecule levels within a sample
• magnetic beads e.g. purification of cell types
• drugs

Question 23

What is a main property of antibodies that allows them to be used as diagnostic tools?

Answer 23

Unique specificity for target antigens

Question 24

What scenarios can manufactured antibodies be used for?

Answer 24

• blood group serology
• immunoassays
• immunodiagnosis

Question 25

What happens in ELISA (enzyme linked immunosorbent assay)?

Answer 25

• clinical samples adhere to plastic plate
• after probed with specific antibody raised against molecule of interest
• antibody is conjugated with enzyme that turns colourless substrate a particular colour
• reference to standard curve, relative absorbance of solution can be used to determine precise levels of molecules being studied.

Question 26

What is flow cytometry?

Answer 26

Technique that allows detection of specific cells (notably lymphocytes) using fluorescently conjugated specific antibodies.

Question 27

What molecules are typically detected by flow cytometry?

Answer 27

• anti CD3+ T cells : pan T cell marker
• anti CD4 + T cells : T helper cells
• anti CD8+ T cells: cytotoxic T cells
• anti CD19+ : B cells
• anti CD56+ : Natural Killer (NK) cells