The term 'Cancer is used to describe a medical condition, where there is:
'Cancer is not a single disease but it refers to a group of diseases which share similar characteristics. Doctors classify cancer on the basis of the tissue from where it originates. For example, the term 'carcinoma' is used for the cancer that originates from the skin or in tissues that line or cover internal organs; and the term 'leukemia' is used for the cancer that starts in the blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced, which enter the blood.
Factors such as tobacco consumption, environmental exposures to carcinogens, certain infections as well as genetic predisposition play an important role in carcinogenesis.
How does Cancer start?
Cancer starts when the genetic material (DNA) of a cell can become damaged or changed, producing changes known as mutations, which affect normal cell growth and division. It is not always clear as to what causes mutations. Some mutations are inherited, some may be due to diet, and others might be caused by exposure to environmental factors, which are referred to as 'carcinogens', such as; some chemicals, tobacco, cigarette smoke etc. When this occurs, cells do not obey the normal life cycle, so the old/ damaged cell do not die, but new ones are still formed leading to larger number of cells than required by the body. These excess cells form a mass of tissue, which is called a 'tumor'.
However every tumor may not be cancerous. The medical terms to differentiate between a tumor and a cancerous tumor are 'benign' and 'malignant.'
Tumor that is not cancerous is referred to as 'Benign' tumor, this.
- Can often be surgically removed
- In most cases rarely there is a recurrence of the condition after surgery
- Remains 'contained' within its organ of genesis and does not invade/ spread to other organs/ part of the body
'Malignant' tumors are 'cancerous'
- Cells in these tumors can invade nearby tissues and spread to other parts of the body
- The spread of cancer from one part of the body to another is called 'Metastasis'
Most cancers are named after the organ or type of cell in which they originate. For example, cancer that begins in the stomach is called stomach cancer.
The extent of growth of cells in the originating tissue, its invasion to nearby lymph nodes and spread to distant organs determines the seriousness, the impact and the line of treatment of the disease, this assessment is referred to as 'Staging' of the cancer.
Usually cancers of the blood & bone marrow such as leukemia do not form tumor.