Session 8: Neoplasia 1 Flashcards
Definition of neoplasm.
An abnormal growth of cells that persists after the initial stimulus is removed. A neoplasm is a type of tumour.
Definition of malignant neoplasm.
Abnormal growth of cells that persists after the initial stimulus is removed AND invades surrounding tissue with potential to spread to distant sites.
Definition of tumour.
Any clinically detectable lump or swelling.
Definition of metastasis.
A malignant neoplasm that has spread from its original site (primary site) to a new non-contiguous site (secondary site).
Define dysplasia.
A pre-neoplastic alteration in which cells show disordered tissue organisation.
What is the main difference between neoplasia and dysplasia?
That dysplasia is reversible. Neoplasia is not.
Give examples of non-neoplastic tumours.
Absess and haematoma
What can neoplastic tumours be subdivided into?
Benign and malignant neoplasms.
What can malignant neoplastic tumours be subdivided into?
Primary or secondary (metastasis)
Benign and malignant neoplasms show different behaviours. Which?
Benign neoplasms remain confined to their site of origin and do not produce metastases.
Malignant noeplasms have the potential to metastatise.
How do benign and malignant neoplasms differ in appearance to the naked eye?
Benign: Tumours grow in a confined local area and so have a pushing outer limit. This makes them less dangerous.
Malignant: Tumours have an irregular outer limit and shape and may show areas of necrosis and ulceration.
How does the degree of differentiation differ in benign compared to malignant neoplasms?
Benign neoplasms are closely resembling the parent tissue meaning that they are well differentiated.
Malignant neoplasms range from well to poor differentiation and may not really resemble the parent tissue.
What are anaplastic cancers?
Cells with no resemblance to any tissue.
How does worsening differentiation show under the microscope?
Individual cells have an:
Increased size
Increased nuclear to cytoplasm ratio
Increased nuclear staining
More mitotic figures
Increasing variation in size and shape of cells + nuclei.
What is hyperchromasia?
What is pleomorphism?
Increased nuclear staining
Increased variation in size, shape of cells and of nuclei.
Clinicians use something called grade when referring to neoplasms.
What is grade?
What does a high grade indicate?
Grade is a term to indicate differentiation. Grade refers to how it looks under a microscope.
A high degree means the neoplasm is poorly differentiated.
Give the grades of the Modified Bloom Richardson grading for breast cancer.
What does each grade involve?
Is grade linked to survival rates?
G1: Tubules in histology
G2: Mitoses in histology
G3: Nuclear pleomorphism in histology
Survival rates fall as the grade increases.
How does grade relate to dysplasia?
Dysplasia also represents altered differentiation. There is mild, moderate and severe dysplasia which indicates worsening differentiation i.e. higher grade.
A high grade dysplasia means a higher risk of it developing into malignant neoplasia.
What is neoplasia caused by?
An accumulation of mutations in somatic cells.
The mutations are caused by initiators which are mutagenic agents and promoters which cause cell proliferation.
X= Initiator O = Promoter
Will the following combinations cause neoplasia?
1: X + X
2: O + O
3: X + O
4: X + X + O
5: X + O + O + O
1: No only initiators cannot cause neoplasia
2: No only promoters will have no mutagenic factor as a predecessor to act on
3: No, there is a need for prolonged exposure of promoters to promote proliferation.
4: No, there is no prolonged exposure of promoters.
5: Yes, there is a need of prolonged exposure to ensure neoplasia.
What is a monoclonal population?
How does it come about?
Can a neoplasm arise from a monoclonal population?
A group of cells produced from a single ancestral cell.
A combination of initiators and promoters result in an expanded monoclonal population.
A neoplasm emerges from a monoclonal population through a process called progression. This is characterised by the accumulation of yet more mutations.
Give example of main initiators.
Chemicals
Infections (e.g. oncogenic viruses)
Radiation
They can also act as promoters.
If not through external mutagenic agents, how can neoplasms mutations come about?
Some neoplasms mutations are inherited.
How do we know neoplasms are monoclonal?
Evidence that neoplasms are monoclonal came from the study of the X-linked gene for the enzyme G6PDH in tumour tissue from women.
Gene has several alleles encoding different isoenzymes.
Early in femal embryogenesis one allele will be randomly inactivated in each cell, this process is called lyonisation.
This means that in heterozygous women that happen to have one allele encoding a heat stable isoenzyme and one a heat labile isoenzyme -> this leads to normal tissue being a mixture of the both.
The problem comes to neoplastic tissue. It express only one isoenzyme which indicates a monoclonal group of cells.
