Health Topic

Cancer

If you or someone you love has been diagnosed with cancer, learn about diagnosis, treatment, risk factors, coping and much more.

Reviewed Reviewed by a registered pharmacistGeneral information

Also called: Carcinoma · Malignancy · Neoplasms · Tumor

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Cancer

Cancer is not just one disease but many diseases. Cancer begins in your cells, which are the building blocks of your body. Usually, your body forms new cells as needed, replacing old cells that die. Sometimes this process goes wrong. New cells grow even when you don't need them, and old cells don't die when they should. These extra cells can form a mass called a tumor.

Tumors can be benign or malignant. Benign tumors aren't cancer, while malignant ones are. Cells from malignant tumors can invade nearby tissues. They can also break away and spread to other parts of your body. The spread of cancer from one part of the body to another is called metastasis. Symptoms and treatment depend on the type of cancer and how advanced it is.

There are more than 100 different types of cancer. Cancer can start almost anywhere in your body. Most cancers are named for where they start. For example, lung cancer starts in the lung, and breast cancer starts in the breast.

Cancer may also be described by the type of cell that formed it, such as sarcoma if cancer begins in your bone and soft tissue. Carcinoma is the most common type of cancer. It is formed by epithelial cells, the cells that cover the inside and outside surfaces of your body.

Cancer is a genetic disease. That means changes in your genes cause it. Changes in your genes are also called gene variants or mutations. Genes are parts of DNA in your cells that you inherit from your parents. However, only some cancers are caused by genes passed down from your parents.

Genetic changes can occur to your genes over your lifetime that affect how your cells function. Usually, your body gets rid of damaged cells before they turn cancerous, but this ability goes down as you age. Other factors that may affect your risk of developing cancer can include:

  • Exposure to ultraviolet (UV) rays from the sun
  • Smoking
  • Your diet
  • Physical inactivity

Cancer symptoms depend on the type of cancer. For example, some of the symptoms that cancer may cause can include:

  • A lump in your breast
  • Blood in your urine (pee) or stool (poop)
  • Bleeding or bruising for no known reason
  • A sore that doesn't heal
  • Trouble swallowing
  • A new mole or a change to a mole you already have

Cancer may cause various symptoms but often doesn't cause pain. Don't wait until you're having pain before seeing your health care provider. See your provider if you have symptoms that don't get better in a few weeks.

There is no single test that can diagnose cancer. The tests ordered are usually based on your symptoms. Your provider may:

  • Ask about your medical history
  • Ask about your family health history, including relatives who have had cancer
  • Do a physical exam
  • Do a screening test such as a mammogram, colonoscopy, or a Pap test
  • Order blood tests or imaging tests

To find out if you have cancer, your provider may order a biopsy. A biopsy is the procedure of removing and examining tissue, cells, or fluids from your body.

Treatment depends on the type of cancer and how advanced it is. Most treatment plans may include surgery, radiation, and/or chemotherapy. Some may involve hormone therapy, immunotherapy or other types of biological therapy, or stem cell transplantation.

It's usually not possible to know exactly why cancer develops in some people but not others. There are some things that you can't control which may increase or decrease your risk of getting cancer, such as inheriting certain genes or your age. But some lifestyle habits may increase your risk of certain types of cancer. Avoid or reduce lifestyle habits such as:

  • Smoking and tobacco use
  • Having too much sun exposure
  • Drinking too much alcohol
  • Not getting enough physical activity
  • Having obesity

It sits within Cancers.

The lead U.S. institute for this subject is the National Cancer Institute.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on Cancer

1,22,178 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

Start Here

  • CancerAmerican Academy of Family Physicians

Diagnosis and Tests

Treatments and Therapies

Prevention and Risk Factors

Living With

Related Issues

Genetics

Statistics and Research

Medical subject headings

Clinicians and researchers index this subject under Neoplasms. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Cancer, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.