What is Cancer?
A Clinical Definition
Cancer is an umbrella term used to describe diseases in in which cells divide without control and are able to invade other tissues. Cancer is not just one disease but many diseases. Clinically, there are more than 100 different types of cancer. Most clinical descriptions of cancers derive from the organ or type of cell in which they start. For example, cancer that begins in basal cells of the skin is called basal cell carcinoma.
Broad clinical definitions of cancer types include:
- Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs.
- Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
- Leukemia - cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.
- Lymphoma and myeloma - cancers that begin in the cells of the immune system.
The Hallmarks of Cancer
In 2000, Douglas Hanahan and Robert Weinberg published a review that synthesized the key molecular definitions of cancer. This review has come to symbolize