S1: What is cancer? Flashcards
What is cancer?
Cancer is the name for a group of diseases characterised by uncontrolled proliferation and spread of abnormal cells
What is a tumour?
The abnormal cells proliferate to form a mass of tissue called a tumour.
What do abnormal cells do?
- multiply and form a tumour
- invade neighbouring tissues and spread throughout the body to form distant tumours
How are cancers classified?
They are classified according to tissue of origin
Name the 4 classes of cancers
Carcinoma (epithelial origin)
Sarcoma (connective tissue)
Lymphoma (lymphoid tissue)
Leukemia (Blooc cells and blood forming cells)
What is the most common class of cancer and why?
Carcinoma’s
This is probably because the epithelia are actively dividing cells and they are most exposed to external damage
What is cell turnover?
This is when a cell grows, matures and then performs its function for a period of time and then die.
The rate of turnover depends on the cell as certain cells don’t turnover (e.g. brain cells).
What are the characteristics of cancer cells?
- Increased cell growth and proliferation in the absence of stimuli
- Decreased cell death
- Decreased cell maturation (decreased differentiation, they behave like immature cells)
- Invade and spread
What are tumours which aren’t cancerous called?
Benign
They do not invade surrounding tisue
e.g. polyps in our colon
What are characteristics of benign tumours?
- Non invasive
- Growth is usually self limiting
- Can grow into malignant cancers
- Can be dangerous if it presses on a vital structure e.g. brain
Benign vs Malignant
If the margins of the tumour are well-defined and growth is entirely local, the tumour is benign (this does not mean they are always harmless).
If the margins of the tumour are poorly defined and the cancerous cells extend into, invade and destroy surrounding tissues then the tumour is malignant.
When diagnosing cancer using histopathology, what are scientists looking for?
- Abnormalities of cells (cytology)
- Abnormalities of tissue structure
- Evidence of invasiveness
How does metastases occur?
As the cell ebcoems more invasive, the cells eat their way through the basement membrane (by proteolysis) and start to spread through the body (become motile)
How does cancer spread to the regional lymph nodes and distant parts of the body?
Local spread occurs through the lymphatic system to the regional lymph nodes
Distant spread to further parts of the body occurs through the blood circulation
What are distant tumours called?
Metastases (singular: metastasis)
How can the origin of a metastases be found?
Looking at cells by doing a biopsy and then looking at a histeopathology
What are the commonest cancer in men and women in the UK?
MEN Prostate Lung Colorectal Bladder
WOMEN Breast Colorectal Lung Ovary Uterus
What are the risk factors that can cause cancer?
- Increasing age
- Chemical factors e.g. tobacco
- Physical factors e.g. ionising/solar radiation
- Viral factors e.g. HPV which is strongly associated with carcinoma in uterine cervix
- Hormonal factors
- Genetics
What is the priamary mechanism of what causes cancer?
- Mutations within the genes of cancer cells
- Dysregulated genes within cancer cells
Mechanism is genetic but it is mostly due to somatic mutations not inherited ones
Several mutations are needed for full malignancy
How are chemical factors, physical factors and age a risk of cancer?
Age is a risk factor, as one gets older there is increased number of mutations over time, so more likely to get multiple mutations in the same cell
Chemical and Physical are a risk as they cause mutations
How hormonal factors a risk for cancer?
They are involved with increased cell turnover (the hormonally driven organ cells are being turned over at a high rate). This high turn over increases the mutation rate
Give an example of how genetics can be a risk for cancer
e.g. an defect in DNA repair being inherited
