2. What is Cancer
In the introduction to this series of articles about cancer we discussed that the word ‘cancer’ describes the various types of conditions that relate to uncontrolled cell division. And so all cancers have this in common.
Each cell of your body contains DNA. In that long strand of DNA is an instruction telling cells how many times to divide. A cell will divide into two identical copies of itself and those new cells will in turn divide again. A cell will continue to divide around fifty times and then it dies and is washed out of the body through the lymphatic system, the blood, excrement or urine. Therefore cells are constantly being renewed in the body.
It is this instruction in the DNA, to stop dividing after a certain amount of divisions that is the cause of what we call a cancer. Without the instruction to stop dividing a cell will just keep going, multiplying indefinitely. Now think about where all these additional cells go if no cells are dying.
The type of cancer depends on which cells of the body are damaged. If smoking has damaged the DNA in your lungs then this will be lung cancer. The mass of new cells multiplying in your body will move around looking for somewhere to settle. With Lymphomas, cells flow through the lymphatic system and collect in lymphnodes under the armpits and groin areas as well as the diaphragm.
They keep collecting and form into lumps which we call tumours. Lymphnodes are the little sacks along the lymphatic system that are usually empty but fill up when you are sick and then are flushed out in due course. These are dead cells that your body has removed in order to keep you healthy, however when cancer cells are looking for space, these sacks are ideal.
Tumours therefore are lumps formed from cells and they can grow to be as large as a tennis ball. A biopsy is often the first treatment to diagnose the type of cancer. A biopsy of a lymphnode tumour can reveal the presence of the Epstein-Barr virus and a consequent diagnosis of Hodgkin’s Lymphoma. So early diagnosis and treatment is always the priority when lumps present themselves.
Cancers are diseases characterised by uncontrolled cell growth. They form tumours made of tissue from cells. With leukaemia cancer doesn’t form into tumours because it travels in the blood stream, but it prohibits the normal blood function by abnormal cell division amassing in the blood.
Let’s repeat that, Cancer is a class of diseases characterised by out-of-control cell growth. It is not a disgusting affliction like the sores of leprosy or the plague and does not carry nasty little germs like the flu, cancer simply means some of your cells have had DNA damage and are now dividing quite normally but they just don’t know when to stop. There are over 200 different types of cancer, and each is classified by the type of cell that is initially affected, so again, if the damaged cells are in your lungs for example, then you have lung cancer.
In summary, Cancer harms the body when altered cells divide uncontrollably to form lumps or masses of tissue called tumours (except in the case of leukaemia where cancer prohibits normal blood function by abnormal cell division in the blood stream). Tumours can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumours that stay in one spot and demonstrate limited growth are generally considered to be benign.
Malignant tumours form when one or both of the following things occur:
1) A cancerous cell moves around the body in the blood stream or the lymphatic system, and destroys healthy tissue in a process called invasion, which in general means it is feeding itself in order to continue dividing, a process called angio genesis that makes new blood vessels to feed itself.
2) A tumour spreads from its place of origin to other parts of the body and grows in a process known as metastasis. Unlike localised cancer, when a tumour metastasises, in particular to an organ such as the liver, it becomes a more serious condition and usually very difficult to treat.
For example, in the example mentioned above for lymphatic cancer, in particular Hodgkins Lymphoma, if the cancer remains localised to the lymphatic system then it will be diagnosed as anywhere up to stage 3b but if metastasised to the bone marrow then the diagnosis will be at stage 4. The treatment for both stages will be different and the latter a more aggressive one.
What are the cancer types
Cancers are divided into five groups according to the type of cell they start from. These are:
- Carcinomas – cancer that begins in the skin or tissues that cover internal organs.
- Lymphomas – cancer that begins in the cells of
the immune system
- Leukaemias – cancer that begins in blood forming tissue such as the bone marrow
- Brain tumours – cancer that begins in the central nervous system
- Sarcomas – cancer that begins in bone, cartilage, fat, muscle, or blood vessels