L32. Dysplasia carinoma sequence: General Principles

Question 1

Define dysplasia

Answer 1

disorderly but NON-NEOPLASTIC proliferation characterised by loss uniformity of cells and architectural organisation
Pleomorphic, hyperchromatic and large nuclei
With mitotic figures clearer
These all seen at all levels (not just as basal stem cells)

Question 2

What are the molecular/genetic basis of malignancy?

Answer 2

Either inherited or acquired (usually a combination of both)

Question 3

What are some genes that can have cancer causing mutations?

Answer 3

Oncogenes
Tumour suppressor genes
DNA repair genes (a subset of TSG)

Question 4

What is generally the occurance (in terms of cell cycle) that is happening in cancer? [2 things]

Answer 4

Cells are being forced out of the G0 stage and forced through the cell cycle. (oncogenes)

Cells are being pushed through different checkpoints in the cell cycle without being corrected or repaired (when they should be put into G0 or killed)

Question 5

Cancers have a complex genome with chromosomal instability (Gross disorder of the chromosomes). Describe this disorder [3]

Answer 5

Multiple copies of chromosomes
Deletions of chromosomes
Translocatons (material from one chromosome moving to another)

Question 6

Describe the mutation in oncogenes

Answer 6

Proto-oncogenes only require ONE HIT = activating mutations (Gain of function)

These drive cells into the cell cycle

Question 7

Describe the mutation in tumour suppressor genes

Answer 7

These are regulatory genes and thus require TWO HITS in order to have a LOSS OF FUNCTION

• requires both copies
• requires an accumulation of mutations

Question 8

What are some classes of proto-oncogenes that could have mutations?

Answer 8

Growth factor receptors = increased growth
Kinases (signal transductions)
Transcription factors in nucleus driving transcription

Question 9

There are three major ways to test abnormalities in these genes. What are the three things that can be looked for?

Answer 9

Translocations: fluorescence can see fusion of different genes
Gene amplification: clusters of nuclear staining in single cells
Sequence mutations (sequencing techniques)

Question 10

What are the various roles of tumour suppressor genes?

Answer 10

Cell cycle regulation
DNA repair
Apoptosis regulation

Question 11

Describe the loss of heterozygosity effect

Answer 11

Some people are born (inherit) single copies of mutations in TSGs and can live for decades with no ill effect. But one mutation in their only remaining copy then complete loss of function and cancer results.
They have a higher risk of developing loss of function TSG

Question 12

Where do the mutations in oncogenes occur vs. tumour suppressor genes?

Answer 12

Oncogenes tend to occur in the active portion of the gene whereas TSG mutations tend to occur in all areas of the gene as they are loss of function

Question 13

What kind of mutations can occur in tumour suppressor genes

Answer 13

Missense, nonsense, frameshift mutations
Large deletions
Loss of heterozygosity
Promotor hypermethylation

Question 14

What are the 6 hallmark features of cancer development?

Answer 14

Inducing angiogenesis
Evasion of apoptosis
Sustaining proliferative signalling
Evading growth suppressors
Activation of invasion and metastasis 
Enabling replicative immunity

Question 15

What is a pre-malignant lesion?

Answer 15

Not yet invasive

But carries high risk of developing malignancy

Question 16

What is intraepithelial neoplasia?

Answer 16

Dysplasia that occurs in the epithelium: confined to the epithelium.

Question 17

Want is carinoma in situ?

Answer 17

A very advanced dysplastic lesion that is not yet malignant. The cancer cells are still within the tissue of origin (inclusive of local lymph nodes)

Question 18

What is transformation?

Answer 18

The movement from a low grade into high grade malignancy via an accumulation of hits into a more aggressive lesion

Question 19

Describe the differences between low grade, moderate dysplasia and high grade dysplasia

Answer 19

Low grade: atypia seen in the basal half with abnormalities in nuclear size, shape and hyperchromasia
Moderate: atypia extends to involve middle third of epithelium
Severe dysplasia shows full thickness atypia and in severe cases is called carcinoma in situ

Question 20

What happens that causes invasive nature of the tumour cells?

Answer 20

Breach of the basement membrane through the underlying stroma and then into vasculature (lymphatics and veins)

Question 21

What four major components of the tumour microenvironment are essential to tumour existence and growth?

Answer 21

1. Some cancer cells may have stem cell like properties
2. Associated stromal cells (especially in the course of invasion)
3. Tumour vascular cells (angiogenesis)
4. Immune infiltrations (can be attacking tumours or attacking normal cells)

Question 22

What is another important microenvironment in terms of cancer?

Answer 22

The metastatic site is important
Some tumours have the propensities to migrate to different sites likely due to microenvironment

Colon cancer to lung and liver
Prostate cancer tends to bone

Question 23

Give three examples of areas that undergo metaplasia in response to chronic injury

Answer 23

1. Chronic reflux oesophagus - Barret’s oesophagus
2. Chronic atrophic gastritis - intestinal metaplasia
3. Chronic inflammation/smoking - squamous metaplasia of lung bronchial epithelium

Question 24

Give an example of physiological metaplasia

Answer 24

The cervical transformation zone: the point where the normal squamous protective epithelium of the ectocervis meets the mucous producing glandular epithelium.

This point varies with the menstrual cycle

It is an unstable immature metaplastic squamous lie mucosa and a site very susceptible to infection with HPV

Question 25

Describe the HPV in terms of dysplasia and cervical cancer

Answer 25

A sexually transmitted infection with many serotypes with high-grade dysplasia and invasive tumour driven by E6 and E7 viral oncogenes

Question 26

HPV has tropism for certain sites in the body, where is this?

Answer 26

Tropism for basal keratinocytes such as basal cells of transformation zone

Question 27

What are the low risk vs. high risk types

Answer 27

types 6 and 11 - major cause of genital warts and mild squamous dysplasia (CIN1)

types 16 and 18 - high risk types causing moderate to severe squamous dysplasia (CIN2-3) and causes squamous cell carcinomas

Question 28

What happens in high risk types HPVs in terms of the genome?

Answer 28

Low risk tend to cause transient infections with viral clearance while High risk tend to integrate with the cellular genome leading to potential tumour production.

Often E6 and E7 oncoproteins are directly interfered with by HPV integration leading to loss of p53 and Rb TSGs and lost p53 apoptosis

Question 29

What is a HPV infected cell called? Describe its features

Answer 29

Koilocyte

Raisenoid hyperchromatic nuclei and perinuclear clearing

Question 30

What is the differences between CIN1, 2 and 3

Answer 30

Respresent cervical intraepithelial neoplasia as mild, moderate and high grade spanning different areas of the epithelium.

Question 31

What two ancillary markers are often used to confirm a high grade lesion?

Answer 31

Ki67 - proliferation marker

P16 - tumour suppressor gene marker

Question 32

Is an inflammatory response normally seen in CIN?

Answer 32

Not normally seen in dysplasia

It is however, a normal inflammatory response to breakage of the basement membrane

Question 33

What do the E6 and E7 oncoproteins bind to and what are the consquence of this binding?

Answer 33

E6 binds to p53 = apoptosis resistance and loss of check points and genomic instability

E7 binds to Rb = disrupts the checkpoint (G1/S) and leads to compensatory upregulation of P16 (marker)

Question 34

In what areas of the body is the intraepithelial nomenclature not seen?

Answer 34

Prostate: no low grade (only high)

In the vulva and oral cavity: no grading, as low grades have potential to cause invasive tumour

Question 35

What is a major predisposition to Barret’s oesophagus?

Answer 35

Long standing gastro-oesophageal reflux

Question 36

What are the 2 diagnostic criteria to Barret’s oesophagus?

Answer 36

Columnar epithelium lining the oesophagus ABOVE the gastro-oesophageal junction

Intestinal metaplasia (may include goblet cells) in the oesophagus

Question 37

Describe the pathogenesis of Barrett’s oesophagus

Answer 37

Chronic GORD –> repetitive mucosal injury by gastric acid and duodenal content (bile and enzymes) –> cellular proliferation in healing –> exposure to carcinogens and eventual reepithelialisation by mucous producing columnar epithelium

Question 38

What does barrett’s oesophagus predispose to?

Answer 38

Oesophageal adenocarcinoma (30-60 fold increase in relative risk)

Question 39

Why don’t we analyse mutations to make diagnoses?

Answer 39

Due to the field effect: generalised exposure of the lower oesophagus to toxins causes mutations in a FIELD of cells (not a single cell) and so chances of picking up this one cell is not likely in early cancer

Question 40

Is there a metaplastic precursor for breast cancer?

Answer 40

No - most sites don’t have a metaplastic precursor (barrets and HPV are exceptions)

Question 41

Barriers required to breech in order to become metastatic is different in different tissues. What are each of the barriers in the following tissue:
Cervix
Oesophagus
Colon
Breast
Prostate

Answer 41

Cervix = basement membrane 
Oeophagus = basement membrane
Colon = muscularis mucosa
Breast = myoepithelial cell layer
Prostate = basal cell layer loss