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Learn about cancer

On this page you will find basic information on cancer. If you would like to know more, you can visit the Cancer Health Channel, a webpage specifically designed for that purpose by the Ministry of Health of the Government of Catalonia. You can find a link to the webpage in the menu on the right-hand side of this page.

The term cancer encompasses around 200 different diseases.

All of them are characterised by the uncontrolled division and growth of cells, which are able to divide within the organ where they originated and, when the tumour becomes malignant, travel through the blood and lymphatic fluid to other organs father away, where they in turn grow, which is when what is known as metastasis occurs.

The prognosis and treatment of cancer greatly vary according to the location of the tumour (prostate, breast, lung, etc.) and the stage at which it is diagnosed (localised, extended, with metastasis, etc.). The smaller and more localised it is, the greater the possibilities for survival are. Currently, and for the first time in the history of humankind, over half of cancers are cured.

All types of cancer are the result of alteration in the genetic material of cells, which causes these cells to stop functioning and become malignant. These alteration may be caused by harmful external agents, such as radiation, chemical products (such as tobacco), infectious agents, and so on, but they may also be caused by errors in the replication of genetic material that go uncorrected.

Tumours that originate due to these causes are termed sporadic or non-hereditary.

Some people are born with an error in their genetic material (DNA) that increases their chances of developing cancer. When this is the main cause of the disease, we say that there is a hereditary predisposition to cancer or hereditary cancer.

People are made up of millions of cells, each one of which has all the information necessary to live. The smallest unit of information is called a GENE (we currently know of over 30,000 genes), and each one of them is responsible for a specific function in our bodies. Genes group together and form chromosomes. All this information is known as genetic material, or DNA. People have 46 chromosomes grouped into pairs, that is, 23 pairs of chromosomes. At the time of conception, when the egg and the sperm join to form the embryo, this embryo INHERITS one chromosome from each of the 23 pairs of the father and one from each of the 23 pairs of the mother, to make its very own 23 pairs of chromosomes.

This genetic information is what gives us our different features, such as eye and skin colour, height, etc. And, of course, it is also in charge of controlling all of the cells of our organism.

A mutation is an alteration in the genetic information (DNA) of an organism, and, therefore, causes a change of feature or function. The genetic unit susceptible to mutation is the gene.


To date, certain genes that intervene in the process of developing cancer have been identified.

In 90-95% of the cases of people with cancer, these individuals were born with genes that operated correctly until one day—due to external factors, errors during normal DNA replication or the passage of time—the genetic material, which had always operated correctly, malfunctioned. When genes suffer alterations or mutation, they cannot carry out their function correctly.

Initially, that a copy of a gene is not operating correctly is not a problem, but if for the same reasons mentioned before, the other copy also malfunctions, this gene ceases to work correctly and, in this case, a normal cell can become cancerous.

That is, for a normal cell to become a cancerous cell, both copies of the gene that control it need to malfunction. This is the standard and most common stop to the start of cancer. These are cases of sporadic cancer.

In the remaining 5-10% of cases, sufferers are born with one of the two genes of the pair altered or mutated (pathogenic mutation), that is, there is a functional error in all the cells of the body. This mutation has been inherited from the father or mother, although it can also be produced at the moment of fertilization. These are cases of hereditary cancer.

This does NOT mean that we have to inherit cancer, rather that we have a higher predisposition or risk of developing the disease than the rest of the population. The tumour only appears if the second copy of the gene, which is healthy, is altered due to the aforementioned external factors.

In order to say that a person or family has a higher risk of suffering from a certain type of tumour than any other individual in the general population, we must first evaluate the family history.

In these types of families, various tumours of the same type or different but related tumours are observed, and various generations are affected (grandfather, father, son). In addition, the age of diagnosis is younger than usual. With a history of this kind, we suspect that we are dealing with a family with a hereditary predisposition.

To have genetic characteristics of this type does not mean that their children will also have them. Depending on the type of inheritance pattern of each gene, the probability of sharing this characteristic with offspring is different:

Autosomal dominant inheritance pattern: for this type of inheritance, the probability of the children also having the mutation is 50%, which means that each time a child is conceived it has a 50% probability of inheriting it, at random and regardless of the sex.

Recessive inheritance pattern: for this type of inheritance, for the children to have the mutation, both the father and the mother must be carriers. That is, they have to inherit an altered gene from each parent. As in the case of autosomal dominant inheritance, the sex of the child makes no difference.

If the person is not a carrier of the genetic mutation present in the family, it cannot pass it down, and his or her children will have the same chances of developing cancer as any other person in the general population.

There are some factors, such as bad habits, that increase the chances of genetic material being damaged, which leads to cancer. Some can be controlled, such as smoking and diet, and others, such as age or inheritance, cannot.

Just as there are factors that increase the risk of cancer, there are habits and measures that enable us to reduce the chances.

The majority of tumours are sporadic, that is, the result of an alteration of the individual’s genes that is not inherited. Only a small part, between 5 and 10%, has a hereditary component. You can find more information in the Genetic Counselling Programme section of the website.

There are three main types of cancer treatment: surgery, radiotherapy and the drug administration (such as chemotherapy). These therapies can be applied individually or mixed and matched. Treatment is determined based on the location, size and stage of the tumour, as well as the overall health of the patient.

Related information

In cases where cancer is suspected, just as with any other disease, first one must see their family practitioner. He or she will assess the case and order the necessary tests, or send you to the correct specialist.

Genetic counselling for hereditary predispositions to cancer is a process in which individuals and their families are informed of their level of risk of developing tumours throughout their lifetimes, based on their own health and family history.

The genetic counselling units discuss:

  • Identification of family members at risk.
  • Measures available for prevention and early diagnosis adapted to said level of risk.
  • Implications of this genetic susceptibility.
  • Possibility of undergoing genetic testing for molecular diagnostics.
  • Probability of carrying or passing down a certain genetic susceptibility to developing tumours.
  • Assessment of the individual and family needs according to the risk situation.
  • Planning of health measures adapted to the level of risk.

In order to correctly assess risk, it is imperative to have a complete family history that includes:

  • Information on at least three generations of the family on both the maternal and paternal side, including cancer diagnoses.
  • Documentation that confirms the diagnosis of any tumour or associated diseases, as well as the age of diagnosis and death and the type of illness.

Genetic counselling can benefit families in which certain types of tumours over various generations occur repeatedly; people diagnosed with a tumour at an early age; and when different types of tumour appear in one family, which are cases in which there is a hereditary cancer predisposition syndrome.

Genetic testing consists in a blood analysis from which DNA is obtained in order to determine if a person is a carrier of a genetic alteration in any of the genes involved in hereditary susceptibility to cancer.

The technique used in genetic testing is complex and to attain results time is often needed.

This test is carried out through blood collection from a member of the family with cancer, and the ideal candidate is chosen based on the individual and family history.

As with any procedure, genetic testing has its benefits, limitations and risks, which individuals and families must assess based on their personal circumstances.

The most noteworthy benefits are related to:

  • Improving how the risk of cancer is used.
  • Avoiding the doubt and anxiety generated by the risk of having cancer.
  • Helping to make decisions regarding behaviour and lifestyle.
  • Informing and advising the rest of the family members.

The main limitations are:

  • Not all high-risk mutations can be detected.
  • Some results are difficult to interpret.
  • Results indicate the likelihood and not the certainty of developing cancer.

Among the most noteworthy risk factors are:

  • Possible psychological disorders, such as anxiety, depression, sense of guilt, etc.
  • A false sense of security.

Positive result: when a mutation causing an alteration in gene function is detected and therefore the main cause of the disease’s occurrence.

A positive result means that testing can be done on other members of the family, with or without cancer, in order to adapt the prevention and/or early detection measures for the disease.

The person in whom the mutation is detected is known as the carrier and has a higher risk of developing cancer than the rest of the general population.

Family members who do NOT have the mutation are known as non-carriers and their risk of developing cancer is the same as that of the general population.

Non-informative result: is when no mutation has been found and, therefore, the rest of the family members cannot be tested, although we offer all the prevention and/or early detection measures for the disease adapted to the risk established by the family history.

Uncertain result: a final possible result is the detection of a mutation but we do not know if it is related to the occurrence of the disease in the family. These are known as uncertain results and also rule out testing family members, but it is taken into account and treated as non-informative.

When you have the result, it is very important that family members be informed of the possibility of visiting the Genetic Counselling Unit for testing and/or to learn about the appropriate prevention and/or early detection measure for each person.

The colon, along with the cecum and the rectum, is part of the digestive tract, specifically the large intestine. The colon is a muscular tube approximately a metre-and-a-half long, the main function of which is to continue absorbing water and mineral nutrients from food and to store faeces.

Colorectal cancer involves the uncontrolled growth of abnormal cells in this part of the intestine.

Colon cancer is one of the most frequent cancers in our field, the second most common type of cancer, both in men and women.

Different risk factors exist in relation to colon cancer. Age is the most important risk factor, as the disease is most frequent among those over 50 and the risk increases progressively after that age. The majority of cases are diagnosed between age 65 and 75, although there are also cases between 35 and 40 years of age. Other risk factors include the consumption of fats and red meat, obesity, tobacco use and frequent alcohol consumption. People with Crohn’s disease, ulcerative colitis and those with personal or family backgrounds of colon cancer are at higher risk than the general population.

Colorectal cancer develops gradually, the majority of times from small lesions called polyps that appear on the inner wall of the intestine. The majority of these polyps are benign, but over time they may become cancerous.

If a polyp is removed in time, the risk of cancer can be prevented.

Most colon and rectal cancers are ‘sporadic’, that is, they are not hereditary and are caused by the alterations in genes that occur over the course of one’s life due to, among other things, environmental factors, age, chance, etc.

Only 5% of all colon cancer cases occur in families with a family history of colon cancer. For these cases a doctor must be consulted, to assess if it is necessary to carry out genetic testing on the family to rule out a hereditary predisposition syndrome.

We suspect hereditary predisposition when:

  • A person is diagnosed with colorectal cancer at a young age, before age 50.
  • There are three or more direct family member (parents, siblings or children) affected by cancer or related tumours (endometrial and uterine, ovarian, brain, etc.).
  • Familial adenomatous polyposis (>20 or more than 100 polyps) is diagnosed.

There are currently two hereditary predisposition syndromes for colon cancer for which genetic testing can be done:

  • Familial polyposis of the colon: an infrequent disease, it represents 1% of all colorectal cancers and is characterised by the appearance in the colon and rectum of hundreds of adenomatous polyps, although polyps can also appear in the stomach and small intestine. It is caused by a genetic alteration in the APC gene.

There is also a lesser form of polyposis in which the person develops polyps throughout the entire gastrointestinal tract, but in a lesser quantity, usually fewer than 100. It is caused by a genetic alteration in the APC or MYH gene.

Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome: the most common form of hereditary colorectal cancer. It accounts for 2-5% of all cases of colon and rectal cancer. It is characterised by the premature development of colorectal cancer and tends to present various lesions at the same time or a second cancer, later on, in the colon and rectum, as well as tumours in other organs (endometrium, stomach, pancreas, urinary tract, ovaries, bile duct and small intestine). The genes MLH1, MSH2 and MSH6 are related with this syndrome and the changes or alterations in these genes are responsible for the majority of HNPCCs. Individuals with HNPCC have a higher risk of colorectal cancer and endometrial or uterine cancer.

Colorectal cancer (CRC) is a tumour that we can prevent. Highly effective strategies are available to reduce both the rate of occurrence/incidence (the number of cases) and of mortality. With this goal in mind, screening programmes try to identify CRC in the early stages. Today, there are tests, such as blood and stool tests and colonoscopies, among others, that allow colon cancer to be detected and diagnosed early on.

In patients with a greater risk of hereditary colorectal cancer, cancer screening tests are recommended, and their frequency will be determined by the doctor or specialist responsible, always taking into account the personal and family history of the patient.

Breast cancer is the most frequent tumour among women and the third among the general population. The most common age for the appearance of the disease is 65.

There are different risk factors related to breast cancer, some of which are connected to our lifestyle, such as tobacco and alcohol consumption, being overweight or the prolonged use of contraceptives. Other risk factors are related to personal characteristics, such as age, as there is an increase in cases after age 50.

The existence of a family history of breast cancer is an important risk factor, but it must be kept in mind that this could be due to risk factors shared among members of the same family.

Various genetic alternations that predispose individuals to breast or ovarian cancer have been discovered. The genes involved in hereditary breast and ovarian cancer are BRCA 1 and BRCA 2. When these genes function correctly, they protect us from the uncontrolled appearance of tumours. However, when they are altered, the risk of developing cancer before age 70 increases by 50-60%.

A family history with various cases of breast cancer does not necessarily imply the presence of hereditary genetic alteration. Only 5-10% of all breast cancer cases diagnosed are hereditary.

We suspect a high risk of breast and ovarian cancer when the following incidents occur in the same family:

  • Two or more first- and second-degree family members with breast/ovarian cancer at an early age (<50).
  • Breast cancer diagnosis before age 30.
  • Breast and ovarian cancer in the same patient.
  • Bilateral breast cancer diagnosis before age 40.

Early diagnosis of a breast tumour means their impact on our health and quality of life can be reduced and favours rapid recovery. Therefore, the Genetic Counselling Unit provides you and your family with all the appropriate monitoring and prevention measures for your level of risk for developing tumours due to an increased predisposition to hereditary cancer, in a personalised manner and using the latest technologies available.

On the Internet we can find a vast number of webpages with information on cancer, but not all of them are reliable. Therefore, it is very important that only those sites run by recognised entities be consulted.

The Ministry of Health of the Government of Catalonia has a Cancer Health Channel where you can find a great deal of information regarding the disease and its treatment.

Related information

Update:  25.10.2011