Histology techniques in the clinic

Question 1

What is pathology

Answer 1

The study of disease - involved in prevention, diagnosis and treatment.

Question 2

What 3 things are required to make a diagnosis?

Answer 2

1. Are the cells benign or malignant
2. The specific cell lineage must be confirmed.
3. Diagnostic sub-type

Question 3

How would a specific cell lineage be determined?

Answer 3

Using immunohistochemistry - using antibodies for specific tissue types.

Question 4

What are resection margins? Why are they used?

Answer 4

The margin of apparently non-tumourous tissue around a tumour that has been surgically resected. If following surgery cancerous cells can be found at the resection margin then not all of the cancer has been resected and further surgery is required.

Question 5

What are the 10 steps from specimen to authorisation report

Answer 5

1) Booking in
2) Cut up - Dissect small specimens
3) Processing - any water content in tissues is removed and replaced with wax under high pressure
4) Embedding - hot wax is poured over the tissue to embed and support it
5) Section cutting - Wax block is cut into thin sections
6) Section staining and coverslipping -
7) Correlation and quality control - Making sure staining/ section is of good quality
8) Microscopy
9) Report
10) Authorisation

Question 6

What immunohistochemical stain is used to separate cancer cells from the supporting stroma?

Answer 6

MNF116 - broad spectrum cytokeratin, binds predominantly to epithelial cell proteins.

Question 7

How do you narrow down the options for a carcinoma of an unknown primary

Answer 7

Use CK7 and CK20 targeted antibodies.

Question 8

What is the cancer likely to be if a section is CK7 and CK20 positive.

Answer 8

Urothelial, ovarian, pancreatic or gall bladder carcinoma

Question 9

What is the cancer likely to be if it is CK7 + and CK20 -

Answer 9

Most likely diagnosis is lung cancer. Could also be breast, thyroid, endometrium, cervical, pancreatic or gall bladder.

Question 10

What is the cancer likely to be if it is CK7- and CK20+

Answer 10

Colorectal carcinoma or merkel cell carcinoma

Question 11

What is the cancer likely to be if it is CK7- and CK20-

Answer 11

Hepatocellular, renal, prostate, head and neck

Question 12

What is the French or FNCLCC grading system

Answer 12

Scored on three factors - differentiation, Mitotic count and tumour necrosis
Grade 1: 2 or 3
Grade 2: 4 or 5
Grade 3 6, 7 or 8

Question 13

For what cancer is the Gleason scoring system used?

Answer 13

Prostate cancer - uses the pattern of the glands

Question 14

For what cancer is the Nottingham prognostic index used?

Answer 14

Breast cancer

Question 15

For what cancer is the Furham system used

Answer 15

Kidney

Question 16

What is the flaw in grading scores?

Answer 16

Resultant phenotype is no representative of the tumour’s genotype. People with the same grade cancer could have hugely variable outcomes.

Question 17

What effect does formalin have on DNA and what is the result of this for genetic investigations of tumour samples

Answer 17

Creates crosslinks in DNA resulting in low input of DNA, also causes DNA degradation which means you are unable to produce robust and reproducible results.

Question 18

Why is the % of neoplastic cells in a sample required for genetic testing

Answer 18

Because different sequencing methods require different overall quantities of neoplastic cells compared to normal ones in a sample.

Question 19

What is the % of neoplastic cells required for COBAS, Sanger and next generation sequencing

Answer 19

COBAS - 1 - 10%
Sanger - 10 - 15%
Next gen - 5 - 10%
general rule is the minimum % of neoplastic cell content should be at least 2x the assays limit of detection.

Question 20

What is a flaw in the way neoplastic cell % is assessed

Answer 20

Its assessed visually so has significant potential for false negatives.

Question 21

What is an alternative to visually assessed neoplastic cell %

Answer 21

Image analysis software - Creates quantitative data which is easy to interpret.