13. Neoplasia Flashcards
What is the definition of a tumour?
A swelling, any clinically detectable lump or swelling
What is the definition of neoplasm?
An abnormal growth of cells that persists after the initial stimulus is removed
What is a benign neoplasm?
Gross and microscopic appearances are considered to be innocent, implying that it will remain localised and will not spread to other sites
What is cancer?
A malignant neoplasm
What is a malignant neoplasm?
An abnormal growth of cells that persists after the initial stimulus is removed and invades surrounding tissue with the potential to spread to distant sites
What is a metastasis?
Malignant neoplasm that has spread from its original site to a new non-contiguous site
What is dysplasia?
Pre-neoplastic alteration in which the cells show disordered tissue organisation
Can be reversible
Can exhibit considerable pleomorphism, with large hyperchromatic nuclei and high nuclear to cytoplasmic ratios
What is the difference between primary and secondary neoplasia?
The original location of the malignant neoplasm is the primary site
The place to which it has spread is the secondary site
What is the difference between benign and malignant in terms of growth?
Benign neoplasms remain confined to their site of origin and do not produce metastases
Malignant neoplasms invade and have the potential to metastasise
What may be present in malignant tumours?
May have ulceration and necrosis
What do benign neoplasms closely resemble?
The parent tissue, well differentiated
What is the differentiation in malignant neoplasms?
Range from well to poorly differentiated, dependent on how closely they resemble the cell of origins
What are cells with no resemblance to any tissue called?
Anaplastic
What happens with worsening differentiation to individual cells?
Increasing nuclear size Increased nuclear to cytoplasmic size Increased nuclear staining Increased mitotic figures Abnormal mitotic figures (Mercedes) Variation in size and shape of cells and nuclei
What is the term grade used for?
Indicate differentiation, a high grade tumour is usually poorly differentiated
What do dysplasia and carcinoma in situ have in common?
Do not invade the basement membrane
Why do we get neoplasia?
Carcinogenesis
Non-lethal genetic damage
How is a tumour formed?
Accumulated mutations in somatic cells
Mutations are cased by initiators - mutagenic agents
Promoters then cause cell proliferation
A tumour is formed by the colonial expansion of a single precursor cell that has incurred genetic damage
Give examples of initiators
Chemicals - smoking, alcohol, diet and obesity
Infectious agents - HPV
Radiation
Inherited mutations
Which genes are mutated in neoplasia?
Growth promoting proto-oncogenes
Growth inhibiting tumour suppressor genes
Genes that regulate programmed cell death
Genes involved in DNA repair
What are proto-oncogenes?
Multiple functions but all participate at some level in signalling pathways that drive proliferation
Mutations that activate these generally cause an excessive increase in one or more normal functions or a completely new function
What are oncogenes created by and what do they do?
Created by mutations in proto-oncogenes and encode proteins called oncoproteins that have the ability to promote cell growth in the absence of normal growth promoting signals
What happens if tumour suppressor genes are damaged?
Normal function is to stop cell proliferation
Generally cause a loss of function
In most instances both alleles must be damaged or transformation to occur
Abnormalities in these genes leads to failure of growth inhibition
What happens if DNA repair genes are damaged?
Loss of function mutations
Contribute indirectly to carcinogenesis
Impair the ability of cell to recognise and repair non-lethal genetic damage in other genes
Affected cells acquire mutations at an accelerated rate
