Cancer is a leading cause of death worldwide. But, it is not a single disease with a single cause and a single type of treatment. There are more than 200 different types of cancer, each with its own name and treatment.
Cells in different parts of the body may look and work differently, but most repair and reproduce themselves in the same way. Normally, cells divide in an orderly and controlled way, nonetheless if for some reason this process gets out of control, the cells carry on dividing, eventually developing into a lump called a tumour. Tumours are either benign (non-cancerous) or malignant (cancerous). A biopsy is normally done to distinguish between a benign or malignant tumour and examining a small sample of cells under a microscope.
Benign tumour: In a benign tumour, the cells do not spread to other parts of the body and so are not cancerous. But, they may carry on growing at the original site, and may cause a problem by pressing on surrounding organs.
Malignant tumour: In a malignant tumour, the cancer cells have the ability to spread beyond the original area of the body. If left untreated, it may spread into surrounding tissue and different parts of the body through the bloodstream or lymphatic system. When the cancer cells reach a new area they may go on dividing and form a new tumour. This is known as a secondary cancer or a metastasis.
Cancers are primarily classified in two ways:
- By site - the part of the body where the cancer first developed (the primary site)
- By cell type - the type of cell the cancer started from.
Cancer types by site
The most common sites in which cancer develops include the:
- Colon and rectum (large bowel).
Cancer types by cell types
Identifying cancer types by cell types may be quite important in understanding how a cancer behaves and responds to treatment as the site where it started.
The human body consists of different types of epithelial cells:
Squamous cells are found in the skin and cover the surface of many parts of the body including the mouth, oesophagus and the airways. The cancers initiating in these cell types are referred to as squamous cell carcinomas.
Adeno cells form the lining of all the glands in the body including those in the breast, bowel, stomach, ovaries and prostate. The cancers initiating in these cell types are referred to as adenocarcinomas.
Urothelial (transitional) cells line the bladder and parts of the urinary system.
Basal cells are found in the skin.
Carcinomas may start in any of these types of cells.
Leukaemia's and lymphomas: Cancers that start in the blood or bone marrow are called leukaemia.
Cancers that start in the lymphatic system are called lymphomas.
Sarcomas: Cancers that start in connective tissue cells are called sarcomas. There are two main types:
- bone sarcomas, which are found in the bones
- Soft tissue sarcomas, which develop in the other supportive tissues of the body.
Cancers that start in other types of cells: Cancer can develop in other types of cells but these cancers are rare. Braincancers are the most common cancers in this group.
Some cancers are more common than others. For e.g. in the UK, lung and prostate cancer are the most common cancers in men, while breast and lung cancer are the most common in women.
Although, the underlying cause for most cancers still remains unknown, certain risk factors increase our chances of developing cancer. For e.g.:
- Poor diet
- Exposure to hazardous substances
- Obesity and lack of exercise.
Signs and symptoms
Cancer can often be managed more easily when it is diagnosed in the early stages. New pharmacological and technological developments have allowed us to cure or control majority of the cancers if detected at the right time in its progression.
Being aware of what is 'normal' in the body can help ensure an early diagnosis of cancer. There are some common signs and symptoms that may alert the fact that something is new or different, for e.g.:
- a lump
- a cough, breathlessness or hoarseness that doesn't go away
- changes in bowel habit
- abnormal bleeding
- changes in a mole
- Unexplained weight loss.
Cancerous lumps can often (but not always) be painless. It is important to remember that lumps and bumps often occur in the body, and most of these will not be cancer.
Coughing, breathlessness and hoarseness
There are many medical conditions that can cause 'chesty' symptoms like coughing and breathlessness (for e.g., infections and inflammations), but in some cases these symptoms may be a sign of lung cancer.
Changes in bowel habit
Symptoms of bowel cancer may include blood in the stools (bowel motion). The blood would usually be dark but can be bright red in colour. Fresh, bright red blood is usually a sign of piles (haemorrhoids). Change in the normal bowel pattern (such as diarrhoea or constipation) for no obvious reason.
Any unexplained bleeding is a sign that there is something wrong. Blood in the urine may be caused by bladder or kidney cancer, although, it can also be caused by infection. Coughing up blood in the sputum may be caused by serious chest infections, but can sometimes be a sign of lung cancer. Vomiting blood can be a sign of stomach cancer, although it can also be due to a stomach ulcer.
Malignant melanoma is a type of skin cancer that often starts with a change in the appearance of normal skin. This can look like an abnormal new mole. Less than a third of melanomas develop in existing moles. It can be difficult to tell the difference between a mole and a melanoma, but any of the following changes should be checked out:
- Asymmetric moles
- Multicolour moles
- Size of the moles (usually more than 7mm in diameter)
- Itching, crusting or bleeding
Unexplained weight loss
Unexplained weight loss over a short period of time should be taken seriously
It has been estimated that more than 1 in 3 people (33%) will develop cancer at some point in their lifetime. Cancers can occur at any age, but the risk of developing cancer increases with age. Cancer isn't common in children or young people.
Three-quarters (75%) of all newly diagnosed cancers occur in people aged 60 or over.
Less than 1 in 100 (1%) of cancers are diagnosed in children, aged 14 years or under.
About 1 in 10 (10%) of cancers are diagnosed in people aged 25-49.
Local treatmentsused to treat cancer in a particular (local) area of the body include surgery and radiotherapy.
Surgery: An operation to remove the tumour is the main treatment for many types of cancer.
Radiotherapy: Radiotherapy uses high energy x-rays to destroy cancer cells.
Systemic treatmentsused to treat cancer in more than one part of the body at a time include chemotherapy, hormonal therapy and biological therapy.
Chemotherapy: Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells.
Hormonal therapy: Hormonal therapies reduce the levels of key hormones in the body or block the hormones from reaching cancer cells, thus stopping/shrinking the cancer.
Biological therapy: Biological therapies work in various ways to destroy cancer cells. They can:
- stimulate the body's defences (immune system) to attack the cancer
- attach to particular types of cells (including cancer cells) in the body so that they die
- interfere with a cancer's ability to grow
- Stop a tumour from making its own blood supply so it can't get the oxygen and nutrients it needs.
Some biological therapies will do just one of these things while others may use two or more of these methods to attack the cancer.
Unfortunately, no treatment is guaranteed to be 100% effective. Sometimes cancer cells which cannot be seen by naked eye or scans can be left behind after treatment and in some people the cancer might come back - sometimes many years later.