Cancer is not a single disease but a collection of related diseases that can occur almost anywhere in the body. In its simplest form, cancer is a disease of genes in the cells of our body. Genes control how our cells work. But, changes in these genes can cause cells to not work, which causes them to grow and be dilived when they shouldn’t — or prevent them from dying when they should die. These abnormal cells can become cancerous.
Understanding how genetic changes cause cancer is a way to understand this disease, while cancer statistics are another way. Cancer statistics help scientists understand the assessment of cancer in society. Statistics can tell us how many people are diagnosed with cancer and how many people die from cancer each year, as well as the number of people who live after a cancer diagnosis.
Set of related diseases
In all types of cancer, some of the cells of the body begin to divide without stopping and spread to the surrounding tissues.
When normal cells age or become damaged, die, and new cells replace them.
and new cells form when they are not needed. These additional cells can be divided without interruption and can form masses called tumors.
Many cancers form solid tumors, which are tissue masses. Blood cancers, such as leukemias, in general do not form solid tumors.
Cancerous tumors are malignant, meaning they can spread to nearby tissues or invade them. In addition, as these tumors grow, some cancer cells may break off and move to distant areas of the body through the circulatory system or lymphatic system and form new tumors away from the original tumor.
In contrast to malignant tumours, benign tumors do not extend to nearby tissues and do not invade them. However, sometimes benign tumors can be quite large. When removed, they usually do not grow back, while malignant tumors do grow back sometimes. Contrary to most benign tumors in other parts of the body, benign brain tumors can endanger life.
What is the cancer?
Cancer is the name that happens to a set of related illnesses. In all the types of cancer, some of the cells of the body begin splitting without stopping and are spread to the textiles of the contour.
The cancer can begin almost in any place of the human body, which is formed of cells trillions. Normally, the human cells grow and split to form new cells as the body needs them. When the normal cells age or are damaged, they die, and new cells the remplazan.
Nevertheless, in the cancer, this tidy process descontrola. As the cells are done more and more abnormal, the old or damaged cells survive when they should die, and new cells form when they are not necessary. These additional cells can split without interruption and can form masses that are called tumors.
Many cancers form solid tumors, which are textile masses. The cancers of the blood, like the leukemia, in general do not form solid tumors.
The cancerous tumors are malignant, what means that they can spread to the nearby textiles or can invade them. Also, after these tumors grow, some cancerous cells can become detached and move to distant places of the body by means of the circulatory system or the lymphatic system
Unlike the malignant tumors, the benign tumors do not spread to the nearby textiles and do not invade them. Nevertheless, sometimes the benign tumors can be quite big. On having been extirpated, generally they do not grow again, while the malignant tumors yes grow again sometimes. Unlike most of the benign tumors in other parts of the body, the benign brain tumors can put the life in danger.
Differences between the cancerous cells and the normal cells
The cancerous cells differ from the normal cells of many ways that allow them to grow without control and become invasive. An important difference is that the cancerous cells are less specializing than the normal cells. This means that, while the normal cells mature in very different cellular types with specific functions, the cancerous cells do not do it. This is a reason by which, unlike the normal cells, the cancerous cells keep on dividing without stopping.
Also, the cancerous cells can ignore the signs that normally they say to the cells that should stop splitting or that should begin a process that is known as a programmed cellular death, or apoptosis, which uses the body to get rid of the cells that are not necessary.
The cancerous cells can have the aptitude to influence the normal cells, the molecules and the blood glasses that surround and feed the cells of a tumor — an area that is known as the microatmosphere. For example, the cancerous cells can induce to the normal cells nearby to which they form blood glasses that give oxygen and nutrients, necessary so that the tumors grow. These blood glasses also withdraw the products of undone from the tumors.
The cancerous cells, often, are also capable of evading the immune system, a network of organs, textiles and specializing cells that it protects to the body against infections and other illnesses. Although ordinarily the immune system eliminates of the body the damaged or abnormal cells, some cancerous cells are capable of “hiding” from the immune system.
The tumors can use also the immune system to be still alive and to grow. For example, with the help of some cells of the immune system that an uncontrolled immune answer prevents ordinarily, the cancerous cells can do in fact that the immune system does not destroy the cancerous cells.
How does the cancer appear
The cancer is a genetic illness — that is to say, it is caused by changes in the genes that control the form as our cells work, especially the form as they grow and split.
The genetic changes that cause cancer can be inherited from the parents. They can happen also in the life of a person like errors result that they happen after the cells split or for the damage of the ADN caused by some exhibitions of the ambience. The environmental exhibitions that cause cancer are the substances, like the chemical compounds in the smoke of tobacco and the radiation, like the beams ultraviolet of the sun. (Our page of Causes and prevention of the cancer has more information).
The cancer of every person has the only combination of genetic changes. The same way as the cancer keeps on growing, additional changes will happen. Even inside every tumor, different cells can have different genetic changes.
In general, the cancerous cells have more genetic changes, like mutations in the ADN, that the normal cells. Any of these changes cannot be related to the cancer; there can be the result of the cancer and not its cause.
“Causers” of cancer
The genetic changes that they contribute to the cancer repairers of the ADN tend to affect three main types of genes — proto-oncogenes, suppressive genes of tumors and genes. These changes are called sometimes “causers” of cancer.
The proto-oncogenes devote themselves to the growth and normal cellular division. Nevertheless, when these genes falter in certain ways or are more active than the normal thing, they can turn into causative genes of cancer (or oncogenes), on having allowed to the cells to grow and to survive when they should not.
The suppressive tumors genes devote themselves to control also the growth and the cellular division. The cells with some alterations in the suppressive tumors genes can split into a form without control.
The genes repairers of the ADN devote themselves to arrange a damaged ADN. The cells with mutations in these genes tend to form additional mutations in other genes. Together, these mutations can cause that the cells become cancerous.
The same way as the scientists have learned more about the molecular changes that result in cancer, certain mutations have been together in many types of cancer. Because of this, the cancers are characterized sometimes according to the types of genetic alterations that one believes are causative, not only for the place of the body where they form and for the form as the cancerous cells are seen to the microscope.
Not cancerous changes in the textiles
Not any change in the textiles of the body is cancerous. Nevertheless, some changes can become cancerous if they do not receive treatment. These are some examples of changes in the textiles that are not cancerous but, in some cases, they need to be watched.
The hiperplasia happens when the cells into a textile split more rapid than the normal thing and the additional cells accumulate or proliferate. Nevertheless, the cells and the form since the textile is organized turn out to be normal to the microscope. The hiperplasia can be caused by several factors or situations, even by the chronic annoyance.
The displasia is the been one more seriously ill than the hiperplasia. In the displasia there is also an accumulation of additional cells. But the cells turn out to be abnormal and there are changes in the form as the textile is organized. In general, as soon as more abnormal the cells and the textile meet, major is the possibility that cancer forms.
Some types of displasia can need that they are watched or that they talk each other. An example of displasia is an abnormal spot (called it snowed displásico) that forms in the skin. One snowed displásico it can turn into melanoma, although they it do not do the majority.
The even more seriously ill been one is a carcinoma in situ. Although sometimes it is called a cancer, the carcinoma in situ is not a cancer because the abnormal cells do not spread beyond the original textile. Namely they do not invade textile of the contour as the cancerous cells do it. But, since some carcinomas in situ turn into cancer, of ordinary they receive treatment.
The carcinomas are the most common types of cancer. They form in the cells epiteliales, which are the cells that cover the internal and external surfaces of the body. There are many types of cells epiteliales, which have often a form as of column when they are seen to the microscope.
The carcinomas that begin in different types of cells epiteliales have specific names:
The adenocarcinoma is a cancer that forms in the cells epiteliales that produce fluids or mucus. The textiles with this type of cells epiteliales are called sometimes glandular textiles. Most of the cancers of bosom, of colon and of prostate are adenocarcinomas.
The carcinoma of basal cells is a cancer that begins in the lowest or basal layer (in the base) of the epidermis, which is the exterior layer of the skin of a person.
The carcinoma of scaly cells is a cancer that forms in the scaly cells, which are cells epiteliales that are under the exterior surface of the skin. The scaly cells cover also many other organs, like the stomach, the intestines, the lungs, the bladder and the kidneys. The scaly cells turn out to be flat, like fish scales, when they are seen to the microscope. The carcinomas of scaly cells sometimes are called carcinomas epidermoides.
The carcinoma of cells of transition is a cancer that forms in a type of textile epitelial called transition epithelium or urotelio. This textile, which it is formed of many layer of cell epiteliales that more big ones or more kidlings can do to themselves, is in the revetment of the bladder, of the uréteres and partly of the kidneys (renal pelvis), and in some other organs. Some cancers of bladder, of the uréteres and of the kidneys are carcinomas of cells of transition.
The sarcomas are cancers that form in the bone and in the soft textiles, even in muscles, textile adipose (grease), blood glasses, lymphatic glasses and in fibrous textile (like sinews and ligaments).
The osteosarcoma is the most common bone cancer. The most common types of sarcoma of soft textile are the leiomiosarcoma, the sarcoma of Kaposi, the malignant fibrous histiocitoma, the liposarcoma and the protuberant dermatofibrosarcoma.
The cancers that begin in the textiles that form the blood in the bone marrow are called leukemia. These cancers do not form solid tumors. Instead of that, a big number of abnormal white globules (cells leucémicas and blastocitos leucémicos) accumulates in the blood and in the bone marrow and displaces to the normal globules of the blood. The low concentration of normal cells of the blood can do that the body takes with difficulty oxygen to the textiles, that it does not control the hemorrhages or that it does not fight the infections.
There are four common types of leukemia, which gather together in accordance with the rapidity with which it worsens the illness (sharp or chronic) and of the type of globule where it begins the cancer (linfoblástico or mieloide).
The linfoma is a cancer that begins in the lymphocytes (cells T or cells B). These are white globules that fight the illnesses and that are part of the immune system. In the linfoma, the abnormal lymphocytes accumulate in the lymphatic ganglions and in the lymphatic glasses, as well as in other organs of the body.
There are two main types of linfomas:
Hodgkin’s Linfoma – The persons who have this illness have abnormal lymphocytes that are called cells of Reed-Sternberg. These cells form, in general, of cells B.
Linfoma not Hodgkin – East is a big group of cancers that begin in the lymphocytes. The cancers can grow with rapidity or with slowness and can form of cells B or of cells T.
Our page on the linfoma has more information.
The multiple mieloma is a cancer that begins in the plasmatic cells, another type of immune cells. The abnormal plasmatic cells, called cells of mieloma, they accumulate in the bone marrow and form tumors in the bones of the whole body. The multiple mieloma calls also mieloma of plasmatic cells and illness of Kahler.