9. Multistep theoryof carcinogens, dysplasia, screening

Question 1

Explain the multistep theory of carcinogenesis

Answer 1

Several mutations required
Each mutation drives a wave of cellular multiplication associated with gradual increase in tumour size, disorganisation and malignancy.
3-6 mutations appear to be required to complete this process

Question 2

What are the different stages of morphological appearance for development of a carcinoma? Molecular changes during this time

Answer 2

Normal epithelium
Hyperproliferative epithelium 
Early adenoma 
Intermediate adenoma
Late adenoma 
Carcinoma

Question 3

What are the two types of cancer critical genes?

Answer 3

Oncogenes

Tumour Suppressor Genes

Question 4

What do onogenes do and what effect do they have?

Answer 4

Stimulate cell division or inhibit cell death and therefore increasing the number of cells

Question 5

What do tumour suppressor genes do and what effect to they have?

Answer 5

Inhibit cell division or stimulate cell death and decrease cell number

Question 6

What is meant by dysplasia and carcinoma in situ?

Answer 6

Represent stages in the cellular journey to invasive malignancy

Question 7

How does dysplasia differ from carcinoma in situ ?

Answer 7

Dysplasia does not present any symptoms and posses so of the abnormalities associated with cancer however there is no invasion of cells into the surrounding tisssue

Question 8

What does dysplasia look like microscopically?

Answer 8

Many features of cancer present sich as haphazard arrangement of cells, crowding of nucleiand increased number of mitotic figures but there is no evidence of invasion

Question 9

If dysplasia is asymptomatic how do we find these patients?

Answer 9

If the lesion involves the skin then it is visible and patients will present to their GP or through screening programmes

Question 10

If dysplasia is asymptomatic how do we find these patients?

Answer 10

If the lesion involves the skin then it is visible and patients will present to their GP or through screening programmes

Question 11

What are some the risks associated with cancer screening programs?

Answer 11

Anxiety and unnecessary investigation in completely healthy patients
Overtreatment of patients with mild dysplasia
Very early treatment of some small very slow growing cancers which may not be of clinical benefit
Missing some cancer causes