Although cancer is often referred to as a single condition, it is actually a general name to group a large number of malignant diseases characterized by the presence of abnormal cells. In this case the signals that makes cells start or stop dividing cannot keep the balance between new cell growth and old cell death, leading to an out of control proliferation of abnormal cells in a part of the body.
How do cells become abnormal? Every organ of the body is composed of tissues that are formed by a collection of cells supported by a structure of proteins
. Cells are very small unities that are the basics of the function of the organ they compose. Every cell has a nucleus
with genes, parts of the DNA
that control its functioning, reproduction and death. DNA is the language of the organism. Genes are sentences that give instructions to the cell. Some genes give the instructions for the programmed cell death, a process where cells with abnormal characteristics commit suicide. What is left of the death cell is recycled by the body and does not cause any damage to the organism. Other genes control cell development and reproduction or cell division. This process is regulated by the interplay of different stimulatory and inhibitory signals where the molecules
say to the cell to start or to stop dividing, respectively. Thanks to these signals there is a good balance between the rates of new cell growth and old cell death that allows the organ to work properly. The DNA in every cell can be damaged because of several factors, like chemicals. The role of certain genes is to give the instructions to repair the DNA rapidly and avoid any unwanted consequence for the cell. Unfortunately, either naturally or as a result of repeated injuries over time, some of the genes mentioned above can get damage in their DNA that cannot be repaired properly. These mutations
can lead a cell to lose control over its normal functioning, reproduction and death. It is generally assumed that if a cell starts to be out of control, this can lead to cancer.
This process is called neoplasia and the resulting mass of tissue is called neoplasm or tumor. Not all neoplasms or tumors are cancer. A tumor can be:
Benign: a benign tumor does not grow in an unlimited manner and does not spread.
Potentially malignant : a pre-cancerous tumor that does not invade surrounding tissues but it is very likely to transform into cancer.
Malignant: a malignant tumor or cancer grows in an unlimited manner, invades and destroys the surrounding tissue and may spread to other parts of the body where cells form new tumors called metastases.
Once the tumor has reached a certain size, it needs blood to survive. Cancer cells deliver messages that tell the surrounding blood vessels that they need to increase their number in order to nourish the tumor.