Cancer is a disease in which cells start to grow out of control. These cells keep on growing to make new cells. They crowd around normal cells. This causes problems in part of body where this disease starts. This can also spread and affect other parts of the body.
These are abnormal cells which divide continuously to destroy body tissues. The cells form a mass called tumor. Tumors can be cancerous or benign.
Cancer is caused by accumulated damage to genes. Such changes may be due to chance or to exposure to a cancer causing substance.
Substances that cause cancer are called carcinogens. A carcinogen may be a chemical substance, such as certain molecules in tobacco smoke.
The causes of this disease may be environmental agents, viral or genetic factors.
We should keep in mind that in majority of cancer cases we cannot attribute the disease to a single cause.
We can divide cancer risk factors into the following categories:
- Biological or internal factors, such as age, gender, inherited genetic defects and skin type.
- Environmental exposure, for instance to radon and UV radiation.
- Occupational risk factors, including carcinogens such as many chemicals and radioactive materials
- Lifestyle-related factors.
- The direct cause of the disease is changes (or mutations) to the DNA in cells. Genetic mutations can be inherited from family members.
These are named as per the area in which they begin and the type of cell they are made of, even if they spread to other parts of the body.
- Carcinoma starts in the skin or the tissues that line other organs.
- Sarcoma is a cancer of connective tissues such as bones, muscles, cartilage, and blood vessels.
- Leukemia is a cancer of bone marrow, which creates blood cells.
- Lymphoma and myeloma are cancers of the immune system of our body.