When is a tumour considered to be benign?
If the neoplastic cells are clustered in a single mass
When is a tumour considered to be malignant?
Once the tumour has undergone metastasis
How many different types of tumours are there?
As many as there are different types of human cells - 200
What does the grouping of a tumour depend on?
The tissue of origin
There is increasing use of molecular definitions to stratify cancers
What are benign tumours of epithelial tissues called?
What are malignant tumours of epithelial cells called?
What are benign connective tissue tumours called?
What are malignant tumours of connective tissue called?
What are benign tumours of lymphoid tissue called?
What are malignant tumours of lymphoid tissue called?
What are malignant tumours of haemopoietic tissues called?
What are malignant tumours of haemopoietic cells called?
What are benign tumours of germ cells called?
What are malignant tumours of germ cells called?
Which of the hallmarks of cancer relate to metastasis?
- Induction of angiogenesis
- Activating invasion and metastasis
What can be determined about tumour metastasis from studies of colon carciogenesis?
Cancer is a multi-hit disease, with accumulation of genetic changes, and the transition to metastasis occurs at the end, once a lot of damage has already been done
What are the steps in the formation of a metastasise?
- Primary tumour formation
- Localised invasion
- Transport through circulation
- Arrest in microvessels of various organs
- Formation of micrometastasis
- Colonisation and formation of macrometasis
What allows localised invasion of a tumour?
Formation of blood vessels
What happens in tumour intravasation?
Interaction of tumour with platelets, lymphocytes, and other blood components
What must be done at all stages of metastasis?
Evasion of the immune system
What allows metastasis to be successful despite it being an inefficient process?
Sheer force of numbers - there are potentially millions of cells circulating
What % of disseminated tumour cells survive to be solitary cells in a secondary organ?
What are the potential fates for solitary cells that get into a secondary organ?
- Viable but dormant
What % of disseminated tumour cells initiate growth into micrometastases?
What % of disseminated tumour cells persist to grow into macrometastases?
Give an example of where other types of cells in the microenvironment are involved in metastasis
Tumour associated macrophages promote breast cancer metastasis
How are macrophages involved in breast cancer metastasis?
A paracrine loop between tumour cells and macrophages is required for tumour cell migration in mammary tumours
Describe the paracrine loop between tumour cells and macrophages required for cell migration in mammary tumours
Tumour cells express CSF-1, which binds to CSF-1 receptor on macrophages and allows them to proliferative and survive. Macrophages express EGF, which binds EGF-receptors on tumour cells
Why is the loss of cell to cell adhesion important in tumour cell metastasis?
Epithelial cells are very tightly organised with strong cell-cell adhesion, which has to be detatched in order for cells to move
What are the different types of adhesions that join cells?
- Tight junction
- Adherens junction