By Ifeyinwa Ugo-Amadi
The body is
made up of numerous cells. These cells make up tissues which make up organs. In
turn, organs make up the ten systems of the body. Normally, these cells grow,
divide to make new cells and die in an organized manner. At childhood and teen
years, normal cells divide at a fast rate allowing the person to grow. As one
becomes an adult, the cells divide just to replace dead or worn out cells or to
repair injuries.
When
something goes wrong and these normal cells start to grow out of control -
cancer is suspected. Cancer is a term used to describe a set of diseases in
which abnormal cells divide without control and can invade other tissues
through the blood and lymph system. This process of spreading to other body
parts is known as metastasis.
Cancers are
named based on the tissue or organ from which they originated. There are over
200 types of cancers with about 20 of them being very common. According to the Centre for Disease Control,
Prostate cancer is the most common cancer among men, breast cancer is most
common among women with lung cancer and colorectal cancer being common to both
sexes. Common amongst children are leukemia and brain cancer. Others are
endometrial, bladder, thyroid, kidney, pancreatic, non-hodgkin lymphoma and
melanoma cancers.
In cancer,
cells refuse to die due to a change or damage in the genetic material (DNA).
These cells grow continuously, forming abnormal cells. Some cancer cells form a
mass of tissues known as tumours that could press hard on other organs, pushing
them aside and replacing them. Cancers such as leukemia does not form tumours.
Tumours can either be benign or malignant.
Benign
tumours are not invasive and do not metastasize. They can slowly grow very
large pressing hard on other tissues but are rarely life-threatening. This is
unlike malignant tumours which are invasive and could spread to other tissues
of the body. Though cells like granulocytes, osteoclasts and trophoblastic
cells have the ability to invade other cells, the invasive growth of malignant
cells is progressive and continuous leading to the destruction of the host
tissue. Cells turn out malignant when they are not recognised by the immune’s
natural killer cells for destruction.
Cancer cells are known for some unique
features. These include
·
Evasion of a process of programmed cell death
·
Insensitivity to anti-growth signals
·
Self-sufficiency in growth signalling
·
Sustainment of a physiological process through which new blood
vessels form from pre-existing ones
·
Activation of metastasis
·
Loss of differentiation
References
http://en.wikipedia.org/wiki/Cancer#Metastasis_2
http://www.cdc.gov/cancer/dcpc/data