What is cancer?
Stages of Cancer
Why does it occur?
Human beings start life as a single cell. Rapid cell division happens in the foetus and through the growing years. After that, cell division stabilises. Cells still divide and new cells are made, but at a slower rate, and largely to replace old and damaged cells. The numbers of cells and the speed with which they divide are carefully controlled. Sometimes, however, the following happen:
- Some cells receive the wrong message and their division becomes uncontrolled.
- These newly developed cells seem like normal cells but are defective and are unable to carry out the functions typical to them.
- The cells multiply at a rate faster than the surrounding tissue and therefore protrude as a lump.
- These dysfunctional cells compete for nutrition with the normal cells. Thus dysfunctional cells grow at the expense of normal cells thereby weakening the entire system
- This abnormal multiplication of body cells keeps on increasing and later spreads to organs like lymph nodes, liver and lung. Ultimately death ensues by the massive invasion of all vital tissues like lung, liver, brain etc.
Types of cancers
Cancers can be broadly classified as:
- Carcinoma: Cancers that form in the cells that cover the skin or line the mouth, throat, lungs and organs;
- Sarcoma: Cancers that start in connective tissues like the bones, muscles and fibrous tissues
- Leukaemia: These are cancers found in the blood, the bone marrow, and the spleen;
- Lymphoma: Cancers of the lymphatic system.
Why does cancer occur?
Cancer could be triggered by various factors like smoking, tobacco chewing, diet, exposure to chemicals or radiation, poor sexual hygiene, some hereditary factors etc.
Different carcinogens are responsible for different types of cancers. (Check the links for specific cancers to learn about their causes). Some cancers, however, cannot be pinned down to a single cause. For some cancers the cause is not known.
What are the symptoms of cancer?
Cancers can take many years to develop. Initially, there may not be any alarming symptoms. Symptoms also depend on the type of cancer. However it is good to watch for the following. The persistence of any of the following is reason enough to go for cancer screening.
- A sore that does not heal
- Unusual bleeding or discharge from any opening in the body
- Thickening or lump in the breast or elsewhere
- Indigestion or difficulty in swallowing
- Change in bowel or bladder habits
- Obvious change in a wart or mole
- Nagging cough or hoarseness of voice
- Unexplained loss of weight or weakness especially in an elderly person.
The great danger of cancer is its insidious, painless onset. Pain is not a sign of cancer; it is a sign of advanced cancer.
Stages of Cancer:
Cancer progresses through several stages and over many years. In each type of cancer, a series of stages has been identified. Treatment depends on the stage at which the disease has been detected.
In general cancer can go through the following stages:
The Initiation Stage:
This is when the cancer-causing agent acts on the chromosomes of the cell. Cancer cannot be identified at this stage.
The Latent Stage:
This can last for many years. The cells are dividing slowly, in an abnormal way. But the disease is not visible.
The Progression Stage:
In this stage the cancer grows rapidly. This may be due to continued exposure to carcinogens or due to the action of some other factor (called a co carcinogen) which catalyses the spread of cancer.
Repeated division of abnormal cells often results in a lump called a tumour. All tumours need not be cancerous. Non cancerous tumours are called benign tumours and these do not spread. Cancerous tumours are called malignant tumours. These spread by infiltration, or pushing through the surrounding cells. In time, these cells push through the tissue and reach a blood vessel or a lymph vessel through which they can circulate and settle in other parts of the body as secondary cancers. This process is called metastasis.