A caregiver providing comfort to a cancer patient


Cancer is a group of over 200 different diseases in which abnormal cells multiply uncontrollably, destroying body tissues or functions. Cancer can form in almost any place in the body and each cancer is named for the tissue type or organ in which it begins. 

The most common types of cancer (other than basal cell skin cancer and squamous cell skin cancer) are breast cancer, lung cancer, prostate cancer, colon and rectal cancer, and melanoma.

Cancer has various symptoms and is treated in different ways depending on the type. Treatments include surgery, chemotherapy, radiation, and immunotherapy.

One in two men and one in three women are expected to develop cancer (not including skin cancer) over the course of a lifetime.

Frequently Asked Questions

  • What causes cancer?

    For a normal cell to become a cancer cell, a series of genetic mutations needs to take place. Environmental or medical radiation, carcinogens, infections, genetic makeup, can raise your risk of mutations. Some substances and exposures directly damage DNA, while lifestyle factors (e.g. poor diet or lack of physical activity) can increase cancer risk by decreasing immune defenses. Recent data shows that the metastatic process is mainly caused by epigenetic factors.

  • Does nicotine cause cancer?

    Whether or not nicotine directly causes cancer remains unclear, but it’s well established that it’s an addictive ingredient in tobacco products. Research also suggests that nicotine may play a role in accelerating cancer growth. Smoking tobacco or using smokeless tobacco products exposes you to cancer-causing substances and can weaken the immune system, making it harder to fight the disease.

  • How does cancer kill you?

    Cancer cells can divide uncontrollably and may locally invade or spread at distance and affect important organs, such as the lungs or liver, or interfere with body functions and systems that are essential for survival. Cancer cells are also good at evading the immune system and can go undetected by the body’s built-in defenses.

  • How many stages of cancer are there?

    Most types of solid cancer have four stages. Stage 1 is the least advanced and stage 4 is the most advanced with the worst prognosis. A common system that is used to determine the stage of solid tumors is the TNM system. It assigns values after tests have evaluated the primary tumor (T value), whether or not it has spread to lymph nodes (N value), and whether or not it has spread to other areas of the body (M value).

  • How do you prevent cancer?

    Things you can do to help reduce your risk of cancer are to quit or avoid smoking, limit alcohol, exercise regularly, use sun protection, eat a healthy diet high in fruits and vegetables and low in red meat, practice safe sex, and check your home for radon to see if you need a radon mitigation system.

  • Can a blood test detect cancer?

    They can contribute to a cancer diagnosis, but, in general, are not used to definitely diagnose. Tests may include a complete blood count, a blood chemistry profile, tumor markers, and circulating tumor DNA (currently used only for research purposes). In some forms of blood cancer, other tests like flow cytometry, immunoelectrophoresis, and cytogenetic analysis are used.

  • Is cancer hereditary?

    Most cancers are related to gene mutations that are acquired and are not inherited. However, in 5% to 10% of cases, cancer is related to a family cancer syndrome that can be inherited. Inherited family syndromes are often mutations in tumor suppressor genes that control how quickly cells divide and when they die.

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Page Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. American Cancer Society. Lifetime risk of developing or dying from cancer. Updated January 13, 2020.

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  5. Sanner T, Grimsrud TK. Nicotine: carcinogenicity and effects on response to cancer treatment – a review. Front Oncol. 2015;5. doi:10.3389/fonc.2015.00196

  6. American Cancer Society. Questions people ask about cancer. Updated 

    National Cancer Institute. What is cancer? Updated February 9, 2015.

  7. American Cancer Society. Family cancer syndromes. Updated January 4, 2018.

Additional Reading