Cancer - symptoms and causes (2023)


Cancer refers to any of a large number of diseases characterized by the development of abnormal cells that divide without control and have the ability to infiltrate and destroy normal body tissue. Cancer generally has the ability to spread throughout the body.

Cancer is the second cause of death in the world. But survival rates are improving for many types of cancer, thanks to improvements in cancer detection, treatment, and prevention.


The signs and symptoms caused by cancer vary depending on the part of the body affected.

Some general signs and symptoms associated with, but not specific to, cancer include:

  • Fatigue
  • Lump or area of ​​thickening that can be felt under the skin
  • Weight changes, including unintentional loss or gain
  • Skin changes, such as yellowing, darkening, or redness of the skin, sores that won't heal, or changes in existing moles
  • Changes in bowel or urinary habits
  • Persistent cough or shortness of breath
  • Difficulty to swallow
  • hoarseness
  • Persistent indigestion or discomfort after eating
  • Persistent and unexplained muscle or joint pain
  • Persistent, unexplained fever or night sweats
  • Unexplained bleeding or bruising

When to see a doctor

Make an appointment with your doctor if you have persistent signs or symptoms that worry you.

If you don't have any signs or symptoms, but you are concerned about your cancer risk, discuss your concerns with your doctor. Ask what cancer screening tests and procedures are right for you.

Book an appointment at the Mayo Clinic


Cancer is caused by changes (mutations) in the DNA within cells. The DNA within a cell is packaged into a large number of individual genes, each of which contains a set of instructions that tell the cell what functions to perform, such as how to grow and divide. Errors in the instructions can cause the cell to stop its normal function and can allow a cell to become cancerous.

What do genetic mutations do?

A genetic mutation can tell a healthy cell to:

  • Allow rapid growth.A genetic mutation can tell a cell to grow and divide more quickly. This creates many new cells that have the same mutation.
  • Inability to stop uncontrolled cell growth.Normal cells know when to stop growing so that you have the correct number of each type of cell. Cancer cells lose the controls (tumor suppressor genes) that tell them when to stop growing. A mutation in a tumor suppressor gene allows cancer cells to continue to grow and accumulate.
  • Making mistakes when repairing DNA errors.DNA repair genes look for errors in a cell's DNA and make corrections. A mutation in a DNA repair gene can mean that other errors are not corrected, causing cells to become cancerous.

These mutations are the most common found in cancer. But many other gene mutations can contribute to causing cancer.

What causes genetic mutations?

Genetic mutations can occur for many reasons, for example:

  • Genetic mutations you were born with.You can be born with a genetic mutation that you inherited from your parents. This type of mutation is responsible for a small percentage of cancers.
  • Genetic mutations that occur after birth.Most gene mutations occur after birth and are not inherited. Several forces can cause genetic mutations, including smoking, radiation, viruses, cancer-causing (cancer-causing) chemicals, obesity, hormones, chronic inflammation, and lack of exercise.

Gene mutations often occur during normal cell growth. However, cells contain a mechanism that recognizes when an error has occurred and fixes it. Occasionally, an error is missed. This can cause a cell to become cancerous.

How do genetic mutations interact with each other?

The genetic mutations you are born with and the ones you acquire throughout your life work together to cause cancer.

For example, if you have inherited a genetic mutation that predisposes you to cancer, it does not mean that you will definitely get cancer. Instead, you may need one or more gene mutations to cause cancer. Your inherited gene mutation may make you more likely than other people to develop cancer when exposed to a certain cancer-causing substance.

It is not clear how many mutations must accumulate for cancer to form. This is likely to vary between cancer types.

More information

  • Cancer treatment at the Mayo Clinic
  • Myths about the causes of cancer.

Risk factor's

Although doctors have some idea of ​​what can increase cancer risk, most cancers occur in people who have no known risk factors. Factors known to increase the risk of cancer include:

Your age

Cancer can take decades to develop. This is the reason why most people diagnosed with cancer are 65 years or older. Although it is more common in older adults, cancer is not an exclusive disease of adults: cancer can be diagnosed at any age.

your habits

Certain lifestyle choices are known to increase the risk of cancer. Smoking, drinking more than one drink a day for women and up to two drinks a day for men, excessive sun exposure or frequent sunburn, obesity, and unprotected sex can all contribute to cancer.

You can change these habits to reduce your cancer risk, although some habits are easier to change than others.

your family history

Only a small proportion of cancers are due to a hereditary condition. If the cancer runs in your family, mutations may be passed from one generation to the next. You may be a candidate for a genetic test to see if you have inherited mutations that may increase your risk of certain types of cancer. Remember that having an inherited gene mutation does not necessarily mean that you will get cancer.

Your health conditions

Some chronic health conditions, such as ulcerative colitis, can significantly increase the risk of developing certain types of cancer. Talk to your doctor about your risk.

your environment

The environment around you may contain harmful chemicals that can increase your risk of cancer. Even if you don't smoke, you can still breathe in secondhand smoke if you go to a place where people smoke or if you live with someone who smokes. Chemicals in your home or workplace, such as asbestos and benzene, are also associated with an increased risk of cancer.


Cancer and its treatment can cause a number of complications, including:

  • Insect.Pain can be caused by cancer or by cancer treatment, although not all cancers are painful. Medications and other approaches can effectively treat cancer-related pain.
  • Fatigue.Fatigue in people with cancer has many causes, but it can often be controlled. Fatigue associated with chemotherapy or radiotherapy treatments is common but is usually temporary.
  • Labored breathing.Cancer or cancer treatment can cause a feeling of shortness of breath. Treatments can bring relief.
  • Nausea.Certain types of cancer and cancer treatments can cause nausea. Sometimes your doctor can predict if your treatment is likely to cause nausea. Medicines and other treatments can help prevent or lessen nausea.
  • Diarrhea or constipation.Cancer and cancer treatment can affect your intestines and cause diarrhea or constipation.
  • Weightloss.Cancer and cancer treatment can cause weight loss. Cancer robs normal cells of food and deprives them of nutrients. This is often not affected by the number of calories or the type of food eaten; it is difficult to treat. In most cases, the use of artificial nutrition through tubes in the stomach or into a vein does not help to alter weight loss.
  • Chemical changes in your body.Cancer can upset the body's normal chemical balance and increase the risk of serious complications. Signs and symptoms of chemical imbalances can include excessive thirst, frequent urination, constipation, and confusion.
  • Brain and nervous system problems.Cancer can press on nearby nerves and cause pain and loss of function in a part of the body. Cancer that affects the brain can cause headaches and signs and symptoms similar to those of a stroke, such as weakness on one side of the body.
  • Unusual reactions of the immune system to cancer.In some cases, the body's immune system can react to the presence of cancer by attacking healthy cells. Called paraneoplastic syndromes, these very rare reactions can cause a variety of signs and symptoms, including difficulty walking and seizures.
  • Cancer that spreads.As the cancer progresses, it can spread (metastasize) to other parts of the body. Where the cancer spreads depends on the type of cancer.
  • Cancer coming backCancer survivors have a risk of cancer recurrence. Some types of cancer are more likely to come back than others. Ask your doctor what you can do to reduce the risk of cancer recurrence. Your doctor can design a follow-up care plan for you after your treatment. This plan may include regular examinations and exams in the months and years after treatment to detect cancer recurrence.


Doctors have identified several ways to reduce the risk of cancer, such as:

  • Smoking father.If you smoke, stop it. If you don't smoke, don't start. Smoking is linked to several types of cancer, not just lung cancer. Stopping now will reduce your risk of cancer in the future.
  • Avoid excessive sun exposure.The sun's harmful ultraviolet (UV) rays can increase the risk of skin cancer. Limit your exposure to the sun by staying in the shade, wearing protective clothing, or applying sunscreen.
  • Eat a healthy diet.Choose a diet rich in fruits and vegetables. Select whole grains and lean proteins. Limit your intake of processed meats.
  • Exercise most days of the week.Regular exercise is associated with a lower risk of cancer. Try to get at least 30 minutes of exercise on most days of the week. If you haven't been exercising regularly, start slowly and work up to 30 minutes or more.
  • Keep a healthy weight.Being overweight or obese can increase the risk of cancer. Work to reach and maintain a healthy weight through a combination of a healthy diet and regular exercise.
  • Drink alcohol in moderation if you choose to drink.If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women and up to two drinks a day for men.
  • Schedule cancer screenings.Talk to your doctor about which types of cancer screening tests are best for you based on your risk factors.
  • Ask your doctor about vaccinations.Certain viruses increase the risk of cancer. Vaccines can help prevent these viruses, including hepatitis B, which increases the risk of liver cancer, and human papillomavirus (HPV), which increases the risk of cervical and other cancers. Ask your doctor if immunization against these viruses is right for you.

By Mayo Clinic staff

07 December 2022

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