Primary and secondary cancer
Most cancers start in one place. The place where a cancer starts is called the primary site. The cancer that starts there is the primary tumour. For example, if you have cancer that starts in the breast, you have primary breast cancer.
Cancers can spread to distant parts of the body. To do this, cancer cells usually get into the bloodstream or the lymphatic system. (The lymphatic system makes and stores cells that fight infection. There are lymph channels and lymph nodes all over the body.) The blood or lymph carries the cancer cells around the body until they get stuck. They may get stuck in a small blood vessel, or in a lymph node.
Next, cancer starts to grow in this new place. The place where it now grows is called the secondary site. The cancer is called a secondary tumour or metastasis. If your breast cancer spreads to the lungs, for example, you have secondary breast cancer. Your secondary cancer is made from breast cancer cells, not lung cancer cells. So you still have breast cancer, even though it is now in your lungs.
The most common places for secondary cancers to grow are the lungs, liver, lymph nodes, bones, brain and skin. Where a secondary cancer is most likely to develop depends on where the primary cancer was.
Sometimes a patient may get a secondary cancer, but doctors can’t find out where the primary cancer is. This type of cancer is called an unknown primary tumour.
Different types of cancer
Carcinomas
Carcinomas are cancers that start on the surface or lining of a body organ. The surface or lining may be on the inside of the body (for example, the lungs, bowel, bladder, stomach, or uterus) or on the outside (for example, the skin). Around nine out of 10 cancers are carcinomas.
Sarcomas
Cancers that start in the body’s bones, fat, muscles, tendons, cartilage or some other tissues are called sarcomas.
Melanomas
Melanomas are cancers that start in the cells that make our skin colour.
Lymphomas
Lymphomas are cancers that start in cells called lymphocytes. These cells are in the bone marrow and lymph nodes, and they help us to fight infection.
Leukaemias
Cancers of the white blood cells are called leukaemias. We need white cells to fight infection.
Myelomas
Myelomas are cancers of the plasma cells in bone marrow. These cells make antibodies that help us to fight infection.
Nerve cell tumours
Cancers that start in the cells of the brain or the spinal cord are called nerve cell tumours.
Germ cell tumours
Cancers that start in the cells that make sperm (in men) and eggs (in women) are called germ cell tumours.