All cancers start when some cells in the body become abnormal and multiply faster than usual.
These cancer cells can outnumber normal cells in the area and may spread to other parts of the body.
There are many types of cancers, which behave in different ways. This is why the experience of having cancer is not the same for everyone.
Cancer is not a single disease. There are many different types of cancers. They can start almost anywhere in the body and can behave in different ways.
The cancer a person has affects:
- the symptoms they get
- the tests and treatments they need
- their chances of recovery after treatment.
Groups of cancers
The different types of cancers belong to two main groups. These are solid tumours and blood (haematological) cancers.
Solid tumours include many common cancers like breast cancer, bowel cancer and lung cancer.
A tumour is a lump or swelling, but not all tumours are cancers:
- Benign tumours are not cancers – they can cause problems if they press on nearby tissues or organs, but they don’t spread to other parts of the body.
- Malignant tumours are cancers – they can spread into nearby tissues or to other parts of the body.
Surgery is the main treatment for many solid tumours. Other treatments may be recommended if the tumour has spread or to prevent it spreading.
Blood (haematological) cancers
Blood cancers affect the blood, bone marrow or lymphatic system. They include leukaemias, lymphomas and myelomas.
Characteristics of blood cancers include:
- They often start in the bone marrow or the lymphatic system.
- Their cells multiply within the blood or lymphatic system and crowd out the normal cells.
- They stop normal blood cells from performing their functions, like preventing infection or stopping bleeding.
- Some, like lymphomas and myelomas, can form lumps as they spread.
Blood cancers can be treated with chemotherapy, immunotherapy, radiotherapy, targeted therapy or blood and marrow transplant to help bring the cancer under control.
How cancers start
The human body contains billions of cells which are dividing to make new cells all the time.
Sometimes there is a problem when cells divide:
- Some of the new cells are abnormal and don't behave like normal cells.
- They can grow and divide faster, or live for longer.
- The body’s immune system doesn't recognise these cells as abnormal so they keep growing.
- As more and more abnormal cells are made, they start to outnumber normal cells in the area.
- They continue to multiply out of control and form a cancer.
How cancers spread
When cells first become abnormal and form a cancer, this is called a primary cancer.
Cells from the primary cancer can spread:
- into surrounding tissues (local spread)
- to nearby lymph nodes (regional spread)
- through the bloodstream or the lymphatic system to other parts of the body (metastatic spread).
Cells that spread to other parts of the body can grow and form a new cancer. This is called a secondary cancer or a metastasis. The cells in the secondary cancer are the same type as those in the primary cancer.