What is metastasis and why does it occur?

Metastasis is a term that refers to a cancerous focus that has spread to a different organ from which it originated. It is this distribution capacity that makes cancer a deadly disease, as it is estimated that more than 90% of deaths in patients from undiagnosed cancers are due to their metastases.

Today we have before us one of the most feared terms by the general population, because unfortunately cancer is a disease that, far from extinction, is spreading more and more across societies in terms of knowledge and epidemiology. The annual incidence of this disease (number of new cases) is almost 500 patients per 100,000 people. A figure of dizziness.

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Therefore, even if we do not want to look this monster in the eye, it is necessary to know the mechanisms that lead to the death of the patient due to a pathology as strong as cancer With Knowledge is power, and of course, the first weapon to be in able to approach the disease from a medical point of view.

Metastasis: worst result

We can not start talking about metastases without defining some terms when it comes to cancer. This disease responds to a range of related pathologies resulting from the atypical uninterrupted growth of some cells of a tissue, which have spread to other organs over time.

In a carcinogenic process, cell circulation is disrupted and functions atypically, as the cells that are supposed to die do not do so and new cell bodies are formed when they are no longer needed, which produces tumors that unfortunately we know so well. well .

Cancer cells are less specialized than normal cells and ignore the processes of apoptosis (programmed cell death). This, added to the fact that they are usually able to bypass the patient’s immune system, is a cocktail to say the least deadly without proper treatment.

Some figures

The link between metastasis and cancer is absolute, as all metastases come from cancer, but not all cancers end up leading to it . We present some data about this pathology collected by the World Health Organization.

  • Cancer is the second leading cause of death in the world. In 2015 there were almost 9 million deaths. One in six deaths is from cancer.
  • About 70% of deaths from this disease occur in low- and middle-income countries.
  • Smoking is the main risk factor, as it is associated with 22% of deaths in patients with cancerous processes.
  • Cancers like lung cancer, unifying all its variants, represent a relative patient survival rate after five years of 23%.
  • 92% of deaths from undiagnosed cancers are due to their metastases.

As we can see, we are facing a bleak outlook. The cancer rate in women has increased 1% from last year, but even so, more and more is known about the disease and its predisposing risk factors. For example, it is estimated that one-third of cases are associated with a high body index, an inadequate diet, lack of exercise, smoking and alcoholism.

The mechanism of metastasis

Once the foundations of this disease have been laid, the process of metastasis is understood in a much easier way. As we had previously predicted, This is characterized by the migration of cancer cells to a tissue other than where they originate .

Normally, this process begins when these atypical growth cells detach from the original tumor, migrate through the circulatory or lymphatic system, and settle into new tissue, also replicating uncontrollably in it. It is important to note that the new tumor shares characteristics with the former, as they are composed of the same cell types.

Thus, a breast cancer that has spread to the liver is considered a metastatic breast cancer and not a liver cancer. Some of the factors that drive this process are as follows:

  • The type of cancer, as some are more likely to spread than others.
  • Tumor growth rate.
  • Other internal and external factors of the disease.

Also, some types of cancer tend to spread to specific parts of the body. For example, malignant tumor processes in the rectum and colon are more likely to spread to the liver and lungs than to any other part of the body.

The stages of metastasis, on the other hand, can be defined in five simple steps that occur in a “cascade”. These are as follows:

  • Detachment – A tumor cell detaches from the primary tumor and leaves its area.
  • Invasion : Cancer cells infiltrate the stroma and migrate through the basement membrane that makes up the vascular endothelium.
  • Intravasion : Tumor cells enter the vascular system after crossing the extracellular matrix barrier.
  • Extravasation : the passage through which these cell bodies spread to other organs.
  • Sleep These cells can stay “silent” in new tissue for several years before they can be expressed.

As we can see, as if it were a susceptible parasite, cancer cells bypass all the physical barriers needed to be able to penetrate the bloodstream and spread.

What promotes metastasis?

We are faced with a question that does not have an answer as simple as one might expect, because unfortunately, a lot of information in the world of cancer is still unknown to us With literature review articles, for example, pointing out that there is a significant correlation between the probability of metastasis and certain groups of genes present in primary tumor cells (which are expressed, for example, by adhesive proteins, cell motility, and degradative activity of uterine protease).

These genetic changes at the cellular level are probably transient or permanent, prompting a tumor cell to reach a metastatic state. For example, studies have found that a gene located on chromosome 7 may be closely linked to this process. The protein produced by this gene, called the “turn”, is essential for the formation of embryonic tissue, but is completely inactivated when the fetus is already formed.

This protein does not exist in normal adult cells or in those that make up the primary tumor, but appears to be present in metastatic cell bodies. We go further because when metastatic cells are inoculated in laboratory animals with the gene that produces the inactivated “turn”, they develop a primary tumor but not a metastatic phenomenon. When cell bodies are vaccinated with the active gene, the animals develop a primitive tumor and the metastasis itself.

Alsoshtë also discovered that for this frightening process to take place, an angiogenic process is essential, namely the formation of blood vessels around the tumor, which provides it with nutrients and oxygen and allows subsequent transport of the cell to other tissues through the circulation of blood.


As we have seen, We still have a long way to go as a society to understand the mechanisms of cancer and how to fight it With Although studies such as that of the gene encoding the “turn” protein are encouraging, the researchers themselves point out that there are many other regulatory genes with similar properties, which obviously need to be investigated, as they are more than likely to play essential roles in the spread of cancer.

There are also numerous medical works responsible for identifying genes that both stimulate and suppress metastasis, for example, more than 10 years ago the first suppressive gene of the aforementioned “metastatic cascade”, NM1, was discovered.

Despite all these open fronts, human beings are playing a fierce battle against cancer: resources and time are limited, and acquiring knowledge is the first step to being able to fight disease effectively. Of course, the bibliography is extensive and the number of open astronomical investigations, so there is nothing left but to trust the scientific method and wait.

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