First cause of death in France, cancers develop from abnormal cells which multiply in an uncontrolled manner to the detriment of the organism. The mutation of certain genes is at the origin of their appearance.
Each individual is made up of nearly 50,000 billion cells organized into tissues (connective tissue, epithelial tissue, nervous tissue, muscle tissue) which will themselves form organs (heart, brain, lung, skin, etc.). Every day, within each organ, thousands of cells will multiply (by cell division) and others will die (by apoptosis). This constant renewal ensures the proper functioning of the body. It is controlled by thousands of genes that work together to “order” cells to multiply or die depending on the situation.
Precise orchestration that goes wrong
An external aggression (alcohol, tobacco, sun, virus, radiation …) or a genetic predisposition can be at the origin of alterations of the DNA of which the genes are composed. These alterations will sometimes lead to the appearance of mutations. Fortunately, cells have repair systems that allow them to identify and correct these anomalies.
Question : What is a genetic predisposition to cancer ?
Sometimes a mutation affecting a gene involved in the development of tumors or in the repair of DNA damage is present in all of a person’s cells from birth. In this situation, a stage of the tumor process being crossed from the outset, the risk of cancer of this person is higher than that of the general population. This is called “genetic predisposition” to cancer.
When the mutations are too large to be repaired, the cell will self-destruct, by apoptosis. But sometimes, these security systems work poorly or no longer work: the cell will then continue to multiply despite the presence of unrepaired mutations. If the latter affect genes involved in the regulation of cell proliferation or apoptosis, the cell can quickly become uncontrollable and multiply in an anarchic way, leading to the formation of a tumor.
However, as a rule, a cell does not become cancerous when it has one or two acquired genetic abnormalities . It is the accumulation of numerous alterations over time that leads it to acquire the properties of a cancer cell. This partly explains why the frequency of cancers increases with age and with the duration of exposure to mutagens.
Question : What is the difference between a benign tumor and a malignant tumor?
Whether benign or malignant (i.e. cancerous), tumors are formed from cells that multiply in a very sustained manner. But unlike those of cancerous tumors, benign tumor cells retain their functionality. In addition, they do not have the capacity to invade other organs. Benign tumors are therefore generally less dangerous. However, when they compress an organ, some benign tumors must be treated. Others can develop into cancer: intestinal polyps, condyloma of the cervix … These benign tumors are said to be precancerous. They must be removed before the cells become malignant.
Characteristics of a cancer cell
Cells that can lead to the formation of cancer have several special features:
- they are immortal : by actively multiplying without ever dying, they accumulate to form a tumor;
- they do not perform the functions of the normal cells from which they are derived: a breast cancer cell will not perform the functions of a normal breast cell;
- they are able to divert local resources to feed on them : tumors often develop a network of blood vessels which allows them to be directly supplied with oxygen, energy and growth factors. This process is called neoangiogenesis;
- they are able to prevent the body’s immune defenses from attacking them.
The evolution of cancer within the body
Over time, cancer cells continue to accumulate abnormalities. They thus acquire new properties which will allow them to develop locally. They will end up invading all the tissues of the organ in which they were born, then reaching the neighboring tissues: at this stage, cancer is said to be “invasive”.
In addition, some tumor cells can become mobile, detach from the tumor, and migrate through the blood or lymphatic systems to form a secondary tumor elsewhere in the body. We are talking about metastasis . Deaths from cancer are mainly due to damage caused by metastases. This is why it is important to diagnose the disease early, before its dissemination in the body.
Cancer is a generic term that covers different types of malignant tumors. Each of them has a specific name depending on the fabric that gave it birth.
- Carcinomas develop from the epithelium, that is to say from the internal or external covering tissue of certain organs (lung, breast, skin, colon, prostate, etc.).
- Adenocarcinomas have receptors for growth factor HER2, but no receptors for estrogen and / or progesterone (RE- and / or RP- and HER2 +).
- Sarcomas are malignant tumors developed from the so-called support tissues of the body, mainly muscles and bones.
- Lymphomas are malignant tumors that develop mainly in the lymph nodes and lymph vessels, that is to say the tissues in charge of the body’s immune defenses.
- Leukemias are cancers that develop in the bone marrow from cells that normally give birth to white blood cells.