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What is cancer?

Cancer is a generic term for a large group of diseases that can affect any part of the body.1

The defining feature of cancer is the rapid creation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs, referred to as metastasis. Widespread metastases are the primary cause of death from cancer.1

A tumor is a lump or growth. Some lumps are cancer (malignant), but many are not (benign). What makes cancer different is that it can spread to other parts of the body while benign tumors do not. Cancer cells can break away from the site where the cancer started.2

Cancer Types

There are many types of cancer, it can develop anywhere in the body and is named for the part of the body where it started.2

Cancer types by System - Head and Neck Cancer, Digestive System Cancer (i.e. Liver Cancer), Urinary System Cancer (i.e. Bladder Cancer), Lung Cancer, Breast Cancer, Reproductive System Cancer (i.e. Cervical Cancer), Endocrine System Cancer (i.e. Thyroid Cancer), Skin Cancer (i.e. Lymphoma of the Skin), Bone and Soft Tissue Cancer, Eye Cancer, Brain and Nervous System Cancer, Blood and Lymph System Cancer and Rare Cancers.3

How does cancer spread?

When cancer cells break away from a tumor, they can travel to other areas of the body through either the bloodstream or the lymph system. Cancer cells that travel through the bloodstream may to reach distant organs. If they travel through the lymph system, the cancer cells may end up in lymph nodes. Cells that make up a metastasis are the same type of cells as in the primary cancer.2

Know the facts about cancer

Cancer is a leading cause of death worldwide, accounting for nearly 10 million deaths in 2020, or nearly one in six deaths. The most common cancers are breast, lung, colon and rectum and prostate cancers. Many cancers can be cured if detected early and treated effectively.1

Highest number of new cancer cases in 2020:1

Each year, approximately 400 000 children develop cancer. The most common cancers vary between countries. Cervical cancer is the most common in 23 countries.1

The most common causes of cancer death:1

Causes of cancer

Cancer arises from the transformation of normal cells into tumour cells in a multi-stage process that generally progresses from a pre-cancerous lesion to a malignant tumour. This is the result of the interaction between a person’s genetic factors and three categories of external agents, including physical carcinogens (ultraviolet and ionizing radiation), chemical carcinogens (asbestos, components of tobacco smoke, alcohol, aflatoxin and arsenic) and biological carcinogens (infections from certain viruses, bacteria or parasites).1

The incidence of cancer rises with age, due to the overall risk accumulation combined with the tendency for cellular repair mechanisms to be less effective as a person grows older.1

Know the risk factors of cancer

Am I at risk?

Tobacco use, alcohol consumption, unhealthy diet, physical inactivity and air pollution are risk factors for cancer and other noncommunicable diseases. Chronic infections are risk factors for cancer. Hepatitis B and C viruses and some types of HPV increase the risk for liver and cervical cancer. Infection with HIV increases the risk of developing cervical cancer and substantially increases the risk of developing select other cancers such as Kaposi sarcoma.1

Know how to reduce the risk of cancer


The risk of cancer can be reduced by not smoking tobacco, maintaining a healthy body weight, eating a healthy diet, doing physical activity on a regular basis, avoiding or reducing consumption of alcohol, getting vaccinated against HPV and hepatitis B if you belong to a group for which vaccination is recommended.1

Early detection

Mortality is reduced when cases are detected and treated early, through early diagnosis and screening.1

Early diagnosis

Cancer is more likely to respond to treatment and can result in a greater probability of survival with less morbidity when identified early. Being aware of the symptoms of different forms of cancer and the importance of seeking medical advice when abnormal findings are observed, access to clinical evaluation and diagnostic services and timely referral to treatment services.1


Screening aims to identify individuals with a specific cancer or pre-cancer before they have developed symptoms.1 When abnormal tissue or cancer is found early, it may be easier to treat or cure. By the time symptoms appear, the cancer may have grown and spread. This can make the cancer harder to treat or cure.4 When abnormalities are identified during screening, further tests to establish a definitive diagnosis should follow, as should referral for treatment. 1 Screening tests include:4

Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments is taken.

Laboratory tests: Medical procedures that test samples of tissue, blood, urine, or other substances in the body.

Imaging procedures: Procedures that make pictures of areas inside the body.

Genetic tests: A laboratory test in which cells or tissue are analyzed to look for changes in genes or chromosomes.

Related Content 

Breast CancerRenal CancerLung CancerPatient Materials


  1. Cancer. WHO. [Internet]. Available from: Accessed: 19/08/2023.
  2. What Is Cancer? [Internet]. Available from: Accessed: 28/08/2023.
  3. About Lung Cancer. American Cancer Society. [Internet]. Available from: Accessed: 20/08/2023.
  4. Cancer Screening Overview - Patient Version. [Internet]. NIH. Available from: Accessed: 28/08/2023.


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