Normal cells in the body follow an orderly path of growth, division, and death. New cells are formed and they replace the old cells. But when this process goes wrong, new cells keep getting formed even when they are not needed and the old cells do not die their programmed death. Cancer is this uncontrolled growth of cells in the human body. The ability of these cells to migrate from the original site and spread to distant sites makes the problem more grave. There are more than 100 different types of cancers depending on the type of cell that is initially affected. The disease starts causing harm to the body when the uncontrolled growth results in tumours. It is only in the case of leukaemia or blood cancer that it prohibits normal blood function by abnormal cell division in the blood stream. The tumours can grow and interfere with the functions of the digestive, nervous, and circulatory system of the body.
Types of Tumours
Depending upon whether the cancer cells can spread to other parts of the body or not, tumours are of two types:
i) Benign tumours – Benign tumours do not spread to other parts of the body.
ii) Malignant tumours – Malignant tumours can invade normal tissues and spread to other parts of the body.
Benign tumours are a result of abnormal multiplication of some cells that do not carry out their normal functions. Benign cancers tend to grow slowly and do not spread. The tumour can be treated in case they are affecting the normal functioning of the body by putting pressure on a particular organ. However, the chances are rare that these tumours may cause harm.
Unlike benign tumours, malignant tumours are formed of cancer cells, and these cancer cells can invade and damage tissues and organs surrounding the tumour and also break away from the tumour and enter the lymphatic system or the bloodstream to form new tumours in other parts of the body.
It is important to find out whether the tumour is malignant or benign, as the cancerous cells can spread. Malignancy is tested by taking a sample of the affected tissue and checking the behaviour of the cells under the microscope.
If one needs to diagnose cancer, there are two ways:
i) In this the doctor looks for certain changes in cells before they become cancerous. This screening enables prevention or at least control of the disease.
ii) In this type of screening cancer is detected at an early stage. At this point in time there may be no symptoms indicating cancer. This is a common screening carried out to detect breast cancer. It helps to take preventive steps or curative treatment.
Causes of Cancer
Cancer starts developing when certain normal genes start mutating. These gene mutations occur mainly due to a complex mix of factors related to heredity, lifestyle, and environment.
There are certain risk factors that trigger cancerous growth. These factors increase a person’s chances of developing cancer. Certain diets, use of tobacco, alcohol, exposure to ultraviolet radiation, and an exposure to carcinogens in the environment are some of the potential catalysts that may trigger cancer. These risk factors only increase the risk of developing cancer; they don’t always cause the disease.
- Damage or harm done by carcinogens: Carcinogens damage the DNA of oncogenes, the genes that manage the normal restrictions on cell growth.
- Permanent damage: Normally DNA repairs itself. However, if the damage is severe or if the repair system fails, oncogenes can be permanently damaged and the damage can hamper or switch-off their cancer preventing function.
- Cell becomes cancerous: If the oncogene is permanently damaged, there will be abnormal cell growth. The malignancy depends on the nature of the affected cells and the manner in which they grow.
How cancer spreads
Cancer usually spreads when the cells break-off from the tumour and are carried by the blood or lymphatic system to other parts of the body. Local growth occurs through the spread and multiplication of cancer cells in the area adjoining the original site. If the cells look normal and also behave normally and push the local tissues, rather than growing into them, the cancer is behaving in a benign way – even if it grows rapidly. Malignant cancer cells tend to produce substances that help them break into other tissues, growing there and finally breaching the walls of blood vessels, lymphatic vessels, and various important structures.
The blood and the lymphatic system are the main routes through which the cancer cells spreads. Once the walls of blood or lymph vessels are breached, then cancer cells can enter the vessels and be transported to other sites in the body. When they lodge themselves at another place, there are chances that they may give rise to more aggressive cancers, the tumours growing independently of the original tumour. This is known as metastasis, whereas the distant growths are called metastases. As far as spreading of cancer is concerned, it spreads to characteristic places.
There are two types of treatments available for cancer:
- In case of tumour formation, the tumour is removed with the help of surgery
Benign tumours can be removed through surgery. Surgery can be performed to reduce the size of the tumour before going for another treatment or to prevent the tumour from damaging the surrounding tissue.
Radiotherapy is also used to treat cancer. The high-intensity radiation helps in destroying the cancer cells. It may cure the disease completely or at least slow down or prevent further growth. However, these radiations may have severe side-effects like loss of appetite, fatigue, nausea and vomiting etc.
Chemotherapy includes treatment through many different drugs that target damaged or mutated oncogenes, growth factors, and division of cancer cells. However, the drugs used in chemotherapy can cause unpleasant side-effects like nausea, vomiting, tiredness, pain, hair loss etc., as they are highly toxic. Along with the type and stage of the cancer, the success of the treatment also depends on various factors like the age of the patient and his/her general health.