Principles of Malignancy + Cancer Pathogenesis Flashcards
What is a tumour?
Mass of abnormal tissue that arises without obvious cause from pre-existing body cells, and is characterised by a tendency to independent growth
What is a cancer (malignancy)?
Characterise by the unregulated cell growth leading to invasion of surrounding tissues + spread
What is benign?
Lacks the ability to invade neighbouring tissue or spread around the body
BUT doesn’t mean they can’t become a cancer
What is malignant?
Gained the ability to invade surrounding tissues, disseminate to other sites within the body
BUT doesn’t mean always lethal
Describe the features of a benign tumour
Encapsulate edges
No metastasis
No invasion
Cells are good comparison to normal
Low growth rate
Normal nuclei
Not normally life-threatening
Describe the features of a malignant tumour
Irregular edges
Metastasis
Invasion
Cells are variable to normal
High growth rate
Irregular nuclei
Usually life-threatening
How are cancers formed?
Accumulation of errors in vital regulatory pathways
Expansion of cell numbers from a single cell
Different for each cancer/tumour type
Can take many years, even a lifetime
What are the structure of neoplastic cells of malignant tumours?
Reproduce to variable extent
= invade neighbouring tissue environments
What are the structure of stroma cells of malignant tumours?
Connective tissue framework which provides support + nutrition to tumour cells
Growth of tumour depends upon ability to induce blood vessels
Fibroblasts give mechanical support
What is differentiation?
Extent to which neoplastic cells resemble comparable normal cells - BOTH morphologically + functionally
Describe well differentiated tumours
Composed of cells resembling normal cells of tissue of origin
Describe poorly differentiated tumours
Cells lacking resemblance to normal cells of the tissue of origin
What is the TNM classification?
T = tumour size
N = presence + no. of lymph nodes involved
M = metastases
How do you determine the prognosis of malignancy?
Tumour type = origin from normal structure
Grade of differentiation = assessment of aggressiveness
Stage/extent of spread = determined by examination of resected tumour + assessment by imaging techniques
What is the grade?
Degree of histological resemblance to parent tissue
What is the stage?
Anatomical extent of spread
What is histogenesis?
Indicates cell type of origin of tumour
What is a sarcoma?
Connective tissue origin
What is carcinoma?
Epithelial origin
What causes cancer?
Hormones
Genetics
Diet
Parasites
Asbestos
Sun/UV
Viruses - eg. HPV
Ionizing radiation
Cigarettes
What factors influence the incidence of cancer?
Lifestyle = smoking + alcohol (various cancers)
Environmental = UV + radiation
Diet = fatty diets (colonic cancer)
Hormonal = oestrogens (breast + ovarian cancer)
Bacterial = H.pylori (stomach cancer)
Parasitic = schistosomiasis (squamous bladder cancer)
Viral = papillomaviruses (cervical cancer)
Occupational = asbestos (mesothelioma)
Genetic = polymorphisms + mutations
Familial = retinoblastoma
What are somatic mutations?
In nongermline tissues
Non-inheritable
eg. cigarette smoke + viruses
What are germline mutations?
Present in egg or sperm
Are inheritable
Cancer family syndrome
What are oncogenes?
Control cell growth = accelerate cell growth + divisions
Mutation = cancer = constant cell growth
What are tumour suppressor genes?
Check for damages = tell cells to undergo apoptosis = prevent cancer
Mutation = turned off = no error checking
Describe tumorigenesis
Initiation = irreversible genetic change in cell - eg. cigarette smoke
Promotion = further genetic errors + growth rate = pre-neoplastic
Progression = cells gain metastatic potential = tumour
Describe the initiation step of tumorigenesis
Genetic change caused by carcinogen or inherited
Most cells with genetic changes are “deleted” BUT some persist
Errors in genes involved with replication or DNA repair
= pre-neoplastic state
Describe the promotion step of tumorigenesis
Acquiring further genetic changes
Associated with genomic instability + perturbation of oncogenes + tumour suppressor genes
Describe the progression step of tumorigenesis
Acquired changes in cellular pathways
Cells now have metastatic potential
Describe cancer pathogenesis
Normal cell
DNA damage = failure of DNA repair
Mutations in genome of somatic cells
= activation of growth-promoting oncogenes
= alterations of genes that regulate apoptosis
= inactivation of cancer suppressor genes
Expression of altered gene products
= malignant neoplasm
How do we treat cancer?
Surgery
Radiotherapy
Chemotherapy = traditional vs targeted
Treatment aims = curative or palliative
