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Welcome to Britannica School , a safe, up-to-date, and age-appropriate information resource for Elementary, Middle, and High School.

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The Definition of Cancer

Cancer is a disease in which some of the body's cells grow uncontrollably and spread to other parts of the body.

Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and multiply (through a process called cell division) to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place.

Sometimes this orderly process breaks down, and abnormal or damaged cells grow and multiply when they shouldn't. These cells may form tumors, which are lumps of tissue. Tumors can be cancerous or not cancerous ( benign).

Cancerous tumors spread into, or invade, nearby tissues and can travel to distant places in the body to form new tumors (a process called metastasis). Cancerous tumors may also be called malignant tumors. Many cancers form solid tumors, but cancers of the blood, such as leukemias, generally do not.

Benign tumors do not spread into, or invade, nearby tissues. When removed, benign tumors usually don't grow back, whereas cancerous tumors sometimes do. Benign tumors can sometimes be quite large, however. Some can cause serious symptoms or be life threatening, such as benign tumors in the brain.

Differences between Cancer Cells and Normal Cells

Cancer cells differ from normal cells in many ways. For instance, cancer cells:

grow in the absence of signals telling them to grow. Normal cells only grow when they receive such signals.

ignore signals that normally tell cells to stop dividing or to die (a process known as programmed cell death, or apoptosis).

invade into nearby areas and spread to other areas of the body. Normal cells stop growing when they encounter other cells, and most normal cells do not move around the body.

tell blood vessels to grow toward tumors. These blood vessels supply tumors with oxygen and nutrients and remove waste products from tumors.

hide from the immune system. The immune system normally eliminates damaged or abnormal cells.

trick the immune system into helping cancer cells stay alive and grow. For instance, some cancer cells convince immune cells to protect the tumor instead of attacking it.

accumulate multiple changes in their chromosomes, such as duplications and deletions of chromosome parts. Some cancer cells have double the normal number of chromosomes.

rely on different kinds of nutrients than normal cells. In addition, some cancer cells make energy from nutrients in a different way than most normal cells. This lets cancer cells grow more quickly.

Many times, cancer cells rely so heavily on these abnormal behaviors that they can't survive without them. Researchers have taken advantage of this fact, developing therapies that target the abnormal features of cancer cells. For example, some cancer therapies prevent blood vessels from growing toward tumors, essentially starving the tumor of needed nutrients.

How Does Cancer Develop?

Cancer is a genetic disease-that is, it is caused by changes to genes that control the way our cells function, especially how they grow and divide.

Genetic changes that cause cancer can happen because:

of errors that occur as cells divide.

of damage to DNA caused by harmful substances in the environment, such as the chemicals in tobacco smoke and ultraviolet rays from the sun. (Our Cancer Causes and Prevention section has more information.)

they were inherited from our parents.

The body normally eliminates cells with damaged DNA before they turn cancerous. But the body's ability to do so goes down as we age. This is part of the reason why there is a higher risk of cancer later in life.

Each person's cancer has a unique combination of genetic changes. As the cancer continues to grow, additional changes will occur. Even within the same tumor, different cells may have different genetic changes.

When Cancer Spreads

A cancer that has spread from the place where it first formed to another place in the body is called metastatic cancer. The process by which cancer cells spread to other parts of the body is called metastasis.

Metastatic cancer has the same name and the same type of cancer cells as the original, or primary, cancer. For example, breast cancer that forms a metastatic tumor in the lung is metastatic breast cancer, not lung cancer.

Under a microscope, metastatic cancer cells generally look the same as cells of the original cancer. Moreover, metastatic cancer cells and cells of the original cancer usually have some molecular features in common, such as the presence of specific chromosome changes.

In some cases, treatment may help prolong the lives of people with metastatic cancer. In other cases, the primary goal of treatment for metastatic cancer is to control the growth of the cancer or to relieve symptoms it is causing. Metastatic tumors can cause severe damage to how the body functions, and most people who die of cancer die of metastatic disease.

Types of Cancer

There are more than 100 types of cancer. Types of cancer are usually named for the organs or tissues where the cancers form. For example, lung cancer starts in the lung, and brain cancer starts in the brain. Cancers also may be described by the type of cell that formed them, such as an epithelial cell or a squamous cell.

You can search NCI's website for information on specific types of cancer based on the cancer's location in the body or by using our A to Z List of Cancers. We also have information on childhood cancers and cancers in adolescents and young adults.

Here are some categories of cancers that begin in specific types of cells:

Carcinoma

Carcinomas are the most common type of cancer. They are formed by epithelial cells, which are the cells that cover the inside and outside surfaces of the body. There are many types of epithelial cells, which often have a column-like shape when viewed under a microscope.

Carcinomas that begin in different epithelial cell types have specific names:

Adenocarcinoma is a cancer that forms in epithelial cells that produce fluids or mucus. Tissues with this type of epithelial cell are sometimes called glandular tissues. Most cancers of the breast, colon, and prostate are adenocarcinomas.

Basal cell carcinoma is a cancer that begins in the lower or basal (base) layer of the epidermis, which is a person's outer layer of skin.

Squamous cell carcinoma is a cancer that forms in squamous cells, which are epithelial cells that lie just beneath the outer surface of the skin. Squamous cells also line many other organs, including the stomach, intestines, lungs, bladder, and kidneys. Squamous cells look flat, like fish scales, when viewed under a microscope. Squamous cell carcinomas are sometimes called epidermoid carcinomas.

Transitional cell carcinoma is a cancer that forms in a type of epithelial tissue called transitional epithelium, or urothelium. This tissue, which is made up of many layers of epithelial cells that can get bigger and smaller, is found in the linings of the bladder, ureters, and part of the kidneys (renal pelvis), and a few other organs. Some cancers of the bladder, ureters, and kidneys are transitional cell carcinomas.

Sarcoma

Sarcomas are cancers that form in bone and soft tissues, including muscle, fat, blood vessels, lymph vessels, and fibrous tissue (such as tendons and ligaments).

Osteosarcoma is the most common cancer of bone. The most common types of soft tissue sarcoma are leiomyosarcoma, Kaposi sarcoma, malignant fibrous histiocytoma, liposarcoma, and dermatofibrosarcoma protuberans.

Our page on soft tissue sarcoma has more information.

Leukemia

Cancers that begin in the blood-forming tissue of the bone marrow are called leukemias. These cancers do not form solid tumors. Instead, large numbers of abnormal white blood cells (leukemia cells and leukemic blast cells) build up in the blood and bone marrow, crowding out normal blood cells. The low level of normal blood cells can make it harder for the body to get oxygen to its tissues, control bleeding, or fight infections.

There are four common types of leukemia, which are grouped based on how quickly the disease gets worse (acute or chronic) and on the type of blood cell the cancer starts in (lymphoblastic or myeloid). Acute forms of leukemia grow quickly and chronic forms grow more slowly.

Our page on leukemia has more information.

Lymphoma

Lymphoma is cancer that begins in lymphocytes (T cells or B cells). These are disease-fighting white blood cells that are part of the immune system. In lymphoma, abnormal lymphocytes build up in lymph nodes and lymph vessels, as well as in other organs of the body.

There are two main types of lymphoma:

Hodgkin lymphoma - People with this disease have abnormal lymphocytes that are called Reed-Sternberg cells. These cells usually form from B cells.

Non-Hodgkin lymphoma - This is a large group of cancers that start in lymphocytes. The cancers can grow quickly or slowly and can form from B cells or T cells.

Our page on lymphoma has more information.

Multiple Myeloma

Multiple myeloma is cancer that begins in plasma cells, another type of immune cell. The abnormal plasma cells, called myeloma cells, build up in the bone marrow and form tumors in bones all through the body. Multiple myeloma is also called plasma cell myeloma and Kahler disease.

Our page on multiple myeloma and other plasma cell neoplasms has more information.

Melanoma

Melanoma is cancer that begins in cells that become melanocytes, which are specialized cells that make melanin (the pigment that gives skin its color). Most melanomas form on the skin, but melanomas can also form in other pigmented tissues, such as the eye.

Our pages on skin cancer and intraocular melanoma have more information.

Brain and Spinal Cord Tumors

There are different types of brain and spinal cord tumors. These tumors are named based on the type of cell in which they formed and where the tumor first formed in the central nervous system. For example, an astrocytic tumor begins in star-shaped brain cells called astrocytes, which help keep nerve cells healthy. Brain tumors can be benign (not cancer) or malignant (cancer).

Our page on brain and spinal cord tumors has more information.

Other Types of Tumors

Germ Cell Tumors

Germ cell tumors are a type of tumor that begins in the cells that give rise to sperm or eggs. These tumors can occur almost anywhere in the body and can be either benign or malignant.

Our page of cancers by body location/system includes a list of germ cell tumors with links to more information.

Neuroendocrine Tumors

Neuroendocrine tumors form from cells that release hormones into the blood in response to a signal from the nervous system. These tumors, which may make higher-than-normal amounts of hormones, can cause many different symptoms. Neuroendocrine tumors may be benign or malignant.

Our definition of neuroendocrine tumors has more information.

Carcinoid Tumors

Carcinoid tumors are a type of neuroendocrine tumor. They are slow-growing tumors that are usually found in the gastrointestinal system (most often in the rectum and small intestine). Carcinoid tumors may spread to the liver or other sites in the body, and they may secrete substances such as serotonin or prostaglandins, causing carcinoid syndrome.

Our page on gastrointestinal neuroendocrine tumors has more information.

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Explanations about what cancer is, how cancer cells differ from normal cells, and genetic changes that cause cancer to grow and spread.

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Cancer is a large group of diseases that can start in almost any organ or tissue of the body when abnormal cells grow uncontrollably, go beyond their usual boundaries to invade adjoining parts of the body and/or spread to other organs. The latter process is called metastasizing and is a major cause of death from cancer.

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Overview

What is cancer?

Cancer is a large group of diseases with one thing in common: They all happen when normal cells become cancerous cells that multiply and spread.

Cancer is the second most common cause of death in the U.S. But fewer people are dying of cancer now than 20 years ago. Early detection and innovative treatments are curing cancer and helping people with cancer live longer. At the same time, medical researchers are identifying independent risk factors linked to developing cancer to help prevent people from developing cancer.

What is the difference between a normal cell and a cancerous cell?

Normally, cells follow instructions provided by genes. Genes set down rules for cells to follow, such as when to start and stop growing. Cancerous cells ignore the rules that normal cells follow:

Normal cells divide and multiply in a controlled manner. Cancerous cells multiply uncontrollably.

Normal cells are programmed to die (apoptosis). Cancerous cells ignore those directions.

Normal cells for solid organs stay put. All cancerous cells are able to move around.

Normal cells don't grow as fast as cancerous cells.

How does cancer start in your body?

Cancer starts when a gene or several genes mutate and create cancerous cells. These cells create cancer clusters, or tumors. Cancerous cells may break away from tumors, using your lymphatic system or bloodstream to travel to other areas of your body. (Healthcare providers call this metastasis.)

For example, a tumor in your breast may spread to your lungs, making it hard for you to breathe. In some types of blood cancer, abnormal cells in your bone marrow make abnormal blood cells that multiply uncontrollably. Eventually, the abnormal cells crowd out normal blood cells.

How common is cancer?

According to the American Cancer Society, 1 in 2 men and people assigned male at birth (AMAB) and 1 in 3 women and people assigned female at birth (AFAB) will develop cancer. As of 2019, more than 16.9 million people in the U.S. were living with cancer. The most common cancers in the United States are:

Who's affected by cancer?

Almost anyone may develop cancer, but data show cancer cases vary based on race and sex. According to the 2022 Annual Report on Cancer, the disease:

Affects slightly more men and people AMAB than women and people AFAB.

Affects more Black men (AMAB) than people in other racial groups.

Affects more women (AFAB) who are American Indian or Alaska natives than people in other racial groups.

Almost anyone may develop cancer, but it typically affects people aged 60 and older.

Symptoms and Causes

What are cancer symptoms?

Cancer is a complicated disease. You can have cancer for years without developing symptoms. Other times, cancer may cause noticeable symptoms that get worse very quickly. Many cancer symptoms resemble other, less serious illnesses. Having certain symptoms doesn't mean you have cancer. In general, you should talk to a healthcare provider anytime there's a change in your body that lasts for more than two weeks.

First symptoms of cancer

Some common early cancer symptoms include:

Left untreated, cancer may cause additional symptoms, including:

Bruising or bleeding more easily.

Lumps or bumps under your skin that don't go away.

Difficulty breathing.

Difficulty swallowing.

What causes cancer?

Cancer is a genetic disorder. It happens when genes that manage cell activity mutate and create abnormal cells that divide and multiply, eventually disrupting how your body works.

Medical researchers estimate 5% to 12% of all cancers are caused by inherited genetic mutations that you can't control.

More frequently, cancer happens as an acquired genetic mutation. Acquired genetic mutations happen over the course of your life. Medical researchers have identified several risk factors that increase your chance of developing cancer.

Cancer risk factors you can control

Smoking: Smoking cigarettes and cigars and using e-cigarettes increases your chance of developing lung, pancreatic, esophageal and oral cancer.

Diet: Eating high-fat or high-sugar foods can increase your risk for many types of cancer. You're also more vulnerable to disease if you don't get enough exercise.

Environment: Exposure to toxins in your environment - such as asbestos, pesticides and radon - can eventually lead to cancer.

Radiation exposure: Ultraviolet (UV) radiation from the sun significantly increases your risk of developing skin cancer. Over-exposure to radiation treatment can also be a risk factor.

Hormone therapy: Women and people AFAB taking hormone replacement therapy may have an increased risk for breast cancer and endometrial cancer.

How can I reduce my risk of developing cancer?

You can reduce your risk by changing some of your lifestyle choices:

If you smoke or use tobacco, try to stop. Ask a healthcare provider about smoking cessation programs that can help you quit tobacco.

Follow a diet plan that's healthy for you. If you want help managing your weight, ask a healthcare provider about nutritional guidance and weight management programs.

Add exercise to your daily routine. Exercise may boost your immune system so it provides more protection against cancer.

Avoid toxins, including asbestos, radon and pesticides.

Protect yourself against sun damage.

Have regular cancer screenings.

Diagnosis and Tests

How do healthcare providers diagnose cancer?

Healthcare providers begin a cancer diagnosis by doing a comprehensive physical examination. They'll ask you to describe your symptoms. They may ask about your family medical history. They may also do the following tests:

Blood tests

Blood tests for cancer may include:

Complete blood count (CBC): A CBC test measures and counts your blood cells.

Tumor markers: Tumor markers are substances that cancer cells release or that your normal cells release in response to cancer cells.

Blood protein tests: Healthcare providers use a process called electrophoresis to measure immunoglobulins. Your immune system reacts to certain cancers by releasing immunoglobulins.

Circulating tumor cell tests: Cancerous tumors may shed cells. Tracking tumor cells helps healthcare providers monitor cancer activity.

Imaging tests

Imaging tests may include:

Biopsies

A biopsy is a procedure healthcare providers do to obtain cells, tissue, fluid or growths that they'll examine under a microscope. There are several kinds of biopsies:

Needle biopsy: This test may be called a fine needle aspiration or fine needle biopsy. Healthcare providers use a thin hollow needle and syringe to extract cells, fluid or tissue from suspicious lumps. Needle biopsies are often done to help diagnose breast cancer, thyroid cancer or cancer in your lymph nodes.

Skin biopsy: Healthcare providers remove a small sample of your skin to diagnose skin cancer.

Bone marrow biopsy: Healthcare providers remove a small sample of bone marrow so they can test the sample for signs of disease, including cancer in your bone marrow.

Endoscopic or laparoscopic biopsy: These biopsies use an endoscope or laparoscope to see the inside of your body. With both of these methods, a small cut is made in your skin and an instrument is inserted. An endoscope is a thin, flexible tube with a camera on the tip, along with a cutting tool to remove your sample. A laparoscope is a slightly different scope.

Excisional or incisional biopsy: For these open biopsies, a surgeon cuts into your body and either the entire tumor is removed (excisional biopsy) or a part of the tumor is removed (incisional biopsy) to test or treat it.

Perioperative biopsy: This test may be called a frozen section biopsy. This biopsy is done while you're having another procedure. Your tissue will be removed and tested right away. Results will come in soon after the procedure, so if you need treatment, it can start immediately.

Genetic testing

Cancer may happen when a single gene mutates or several genes that work together mutate. Researchers have identified more than 400 genes associated with cancer development. People who inherit these genes from their biological parents may have an increased risk of developing cancer. Healthcare providers may recommend genetic testing for cancer if you have an inherited form of cancer. They may also do genetic testing to do therapy that targets specific cancer genes. They use test results to develop a diagnosis. They'll assign a number or stage to your diagnosis. The higher the number, the more cancer has spread.

How is cancer stage determined?

Healthcare providers use cancer staging systems to plan treatment and develop a prognosis or expected outcome. TNM is the most widely used cancer staging system. T stands for primary tumor. N stands for lymph nodes and indicates whether a tumor has spread to your lymph nodes. M stands for metastasis, when cancer spreads.

What are the four stages of cancer?

Most cancers have four stages. The specific stage is determined by a few different factors, including the tumor's size and location:

Stage I: The cancer is localized to a small area and hasn't spread to lymph nodes or other tissues.

Stage II: The cancer has grown, but it hasn't spread.

Stage III: The cancer has grown larger and has possibly spread to lymph nodes or other tissues.

Stage IV: The cancer has spread to other organs or areas of your body. This stage is also referred to as metastatic or advanced cancer.

Though stages one through four are the most common, there's also a Stage 0. This earliest phase describes cancer that's still localized to the area in which it started. Cancers that are still in Stage 0 are usually easily treatable and are considered pre-cancerous by most healthcare providers.

Management and Treatment

How do healthcare providers treat cancer?

Healthcare providers may use several different treatments, sometimes combining treatments based on your situation. Common cancer treatments include:

Chemotherapy:Chemotherapy is one of the most common cancer treatments. It uses powerful drugs to destroy cancer cells. You may receive chemotherapy in pill form or intravenously (through a needle into a vein). In some cases, providers may be able to direct chemotherapy to the specific area affected.

Radiation therapy:This treatment kills cancer cells with high dosages of radiation. Your healthcare provider may combine radiation therapy and chemotherapy.

Surgery:Cancerous tumors that haven't spread may be removed with surgery. Your healthcare provider may recommend therapy. This treatment combines surgery with chemotherapy or radiation to shrink a tumor before surgery or to kill cancer cells that may remain after surgery.

Hormone therapy:Sometimes, providers prescribe hormones that block other cancer-causing hormones. For example, men and people assigned male at birth who have prostate cancer might receive hormones to keep testosterone (which contributes to prostate cancer) lower than usual.

Biological response modifier therapy:This treatment stimulates your immune system and helps it perform more effectively. It does this by changing your body's natural processes.

Immunotherapy for cancer:Immunotherapy is a cancer treatment that engages your immune system to fight the disease. The treatment may be called biological therapy.

Targeted therapy for cancer: Targeted therapy is a cancer treatment that targets the genetic changes or mutations that turn healthy cells into cancer cells.

Bone marrow transplant: Also called stem cell transplantation, this treatment replaces damaged stem cells with healthy ones. Autologous transplantation uses your supply of healthy stem cells. Allogeneic transplantation uses stem cells donated by another person.

What are cancer treatment side effects?

Healthcare providers work to balance the treatment so it destroys cancer without harmful or lasting side effects. Even so, all cancer treatments have side effects. Some treatments cause side effects that last for years after treatment is completed. Many people benefit from palliative care that eases cancer symptoms and treatment side effects. The most common cancer treatment side effects are:

Outlook / Prognosis

What is the prognosis/outlook for cancer?

Right now, more people are being cured of cancer or living longer with cancer. In general, people with cancer that were diagnosed and treated before it could spread have a good outlook.

But you're unique, and so is your cancer prognosis. Your healthcare providers will base your prognosis on factors such as:

Your overall health.

The type of cancer you have.

The stage of your cancer.

How you may respond to treatment.

Your overall health, the type of cancer that you have, its stage and how you respond to treatment all affect your prognosis.

Your healthcare provider is your best resource for prognosis information. They know your situation and they know you.

What are cancer survival rates?

Survival rates are estimates based on the experiences of large groups of people who have different kinds of cancer. Like prognoses, cancer survival rates vary based on cancer type, stage and treatment. According to the most recent data from the National Cancer Institute, 68% of people with any kind of cancer were alive five years after their diagnosis.

Living With

How do I live with cancer?

Self-care is an important part of living with cancer. Some self-care suggestions include:

Establish good eating and exercise habits. Ask to speak with a nutritionist for healthy menu ideas.

Fatigue is a common symptom and treatment side effect. Pay attention to your body and rest when you need to, not just when you can.

You may be living with cancer for a long time. That's good news, of course, but chronic illness may be challenging. Talking to a mental health professional or finding a support group may help you navigate challenges.

What is cancer survivorship?

If you have cancer, you are a cancer survivor. Cancer survivorship starts the day you receive a cancer diagnosis and continues for the rest of your life. As a cancer survivor, you're likely to experience many challenges or complications.

Cancer that comes back

Sometimes, cancer treatment doesn't eliminate all cancerous cells. Those cells can become new cancerous tumors. Cancer that comes back, or recurrent cancer, may appear at the same place as the original cancer, in nearby lymph nodes or spread to organs and tissues far away from the original site.

Second cancer

A second cancer is a new cancer. People who have second cancers may have cancer in the same organ or area of their body as the first cancer, but it's a different type of cancer from what it was before. They may also have cancer in different areas of their bodies. Second cancers are more common, as more people live longer with cancer.

Cancer fatigue

Cancer fatigue is an overwhelming sense of tiredness that isn't helped by getting more rest. Some people have chronic cancer fatigue that continues after they've finished treatment.

Cancer pain

Some cancer treatments have lasting side effects that may cause pain. One study found that 39% of people who completed cancer treatment had chronic pain. Peripheral neuropathy is an example of pain that may persist after treatment.

Chemotherapy brain fog

Chemotherapy brain fog (chemo brain) happens when cancer or cancer treatment affects your ability to remember or act on information. About 75% of people receiving cancer treatment tell their healthcare providers that they have issues with memory, concentration and their ability to complete tasks.

When should I see my healthcare provider?

Talk to your healthcare provider about any issues you experience while you're undergoing cancer treatment. Call your oncology team if you notice:

A fever of 101 degrees Fahrenheit (38.33 degrees Celsius) or higher.

Severe headaches.

Chills.

Persistent cough.

Shortness of breath (dyspnea).

Sores on your lips or in your mouth.

Sudden weight loss greater than five pounds.

Excessive vomiting (three times an hour for three hours or more).

Blood in your urine (pee) or feces (poop).

Excessive bleeding or bruising.

What questions should I ask my healthcare provider?

Knowledge is power. If you've been diagnosed with cancer, you'll want to gather as much information as you can. Here are some questions to ask your healthcare provider:

What type of cancer do I have?

Has the cancer spread to other areas of my body?

Is my cancer genetic?

What are my chances of survival?

Which treatments do you recommend?

What are the risks and benefits of my treatment?

How long will treatment take?

Will I be able to work during cancer treatment?

Will cancer treatment affect my fertility?

Will I need to stay in the hospital for my treatment?

Would a clinical trial be a good option for me?

A note from Cleveland Clinic
The words "you have cancer" may be one of the hardest things anyone has to hear. Learning you have cancer might make you feel frightened and overwhelmed. Many people feel as if they've lost control of their lives. Your healthcare providers understand all of those feelings. They know a cancer diagnosis is a life-changing event. They also know cancer treatment is a stressful journey. If you have cancer, know your providers will be with you every step of the way.

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Cancer: Symptoms, Stages, Types & What It Is

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Cancer is a large group of diseases with one thing in common: They all happen when normal cells become cancerous cells that multiply and spread. Cancer is the second most common cause of death in the U.S. But fewer people are dying of cancer now than 20 years ago.

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cancer - facts from Kiddle Encyclopedia - visual search engine for kids

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Although there is no cure for cancer yet, detecting and treating the disease at an early stage can significantly improve a person's outlook. The cancers with the highest 5-year relative survival rates include melanoma, Hodgkin lymphoma, and breast, prostate, testicular, cervical, and thyroid cancer.

Cancer is a disease that causes cells to grow and multiply uncontrollably in certain parts of the body. It may start in one part of the body and then spread to other areas. As a result, cancer can have a severe impact on the surrounding tissues and organs.

Despite substantial investment and years of research worldwide, cancer remains the leading cause of death in the United States. The National Cancer Institute estimated that doctors would diagnose 1,806,590 new cases across the U.S. in 2020 and that 606,520 people will die from cancer in this year.

Successful treatment may remove all signs of cancer from a person's body. Doctors describe this as being in remission. However, cancer can return after remission, sometimes many years later.

Curing cancer would mean completely eradicating the condition without it coming back. Although this can happen for some people, there is currently no specific cure for cancer.

Many factors influence the likelihood of successful cancer treatment, including the type of cancer.

To understand the difference in outlook between cancer types, researchers often use a statistic called the 5-year survival rate. This figure refers to the percentage of people who survive for 5 years after the diagnosis of cancer.

The 5-year survival rate does not indicate whether or not treatment has removed all signs of cancer, but it is useful for comparing the relative severity of different types of cancer. It is important to remember that many other factors influence survival, such as how early the doctors detect the disease.

To provide a more accurate estimate of the outlook for cancer, doctors can also refer to 5-year relative survival rates. Relative survival rates compare people with a specific disease to those in the general population without the disease. They take into account the fact that other factors can impact survival.

In this article, we look at the seven types of cancer that have the highest 5-year relative survival rates. These survival rates are primarily for cancers that doctors have diagnosed at an early stage.

The stages describe the size and location of the tumor. Stage 0 refers to the growth of abnormal cells in the breast tissue or lobules within the breast. At this stage, doctors do not consider it to be cancerous, but it can indicate very early signs of cancer.

In stage 1 breast cancer, tiny tumors are present that:

are typically less than 2 centimeters (cm) in size

have not spread to a different area of the body

Doctors can isolate and treat these types of breast cancer before they develop into more severe forms of cancer.

In the early stages of testicular cancer, doctors can remove either one or both of the testicles to treat the condition.

Testicle removal is an effective form of treatment. However, it is significantly less beneficial when cancer has spread.

Thyroid cancer has a 5-year relative survival rate of 98-100 percent at stages 1 and 2. The thyroid is a gland in the neck that produces hormones to support healthy bodily functions.

Most thyroid cancers grow slowly, which allows more time for treatment to take place. Even when cancer spreads into surrounding tissues in the throat, removing the thyroid gland can be an effective method of eradicating it.

Melanoma is a cancer of the skin, and it has a high survival rate because it is easy to detect in this part of the body. It is often possible to identify and treat melanoma in the early stages of its progression, which increases a person's chance of survival.

However, without early detection, melanoma can spread beneath the surface of the skin and become more difficult to remove.

The high relative survival rate of Hodgkin lymphoma is due to it responding well to radiation treatment. This means that the survival rate remains high for people who have more advanced forms of this cancer. However, other types of lymphoma do not respond as well to treatment.

There is currently no cure for cancer. However, successful treatment can result in cancer going into remission, which means that all signs of it have gone. The early detection and treatment of cancer can significantly improve the chances of remission and a person's outlook.

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Top 7 most curable cancers based on 5-year relative survival rate

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There is no cure for cancer, but successful treatment can remove all signs of it. Doctors may base the outlook on the 5-year relative survival rate. This is the percentage of people likely to survive for 5 years after diagnosis compared to people without cancer. Here, we look at seven cancers with high survival rates.

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In 2020, 19 million people around the world received a cancer diagnosis. By 2040, that number is expected to reach 28 million. Poorer countries will be especially hard hit, with an increasing number of cases and more deaths, compared with richer countries.

Cancer research is vital to helping ease this global burden, but where and how research money is spent doesn't always match with where and how help is needed. To get a clearer picture of where cancer research funding is spent, we collected and compiled data covering public and charitable cancer research investments, globally, between 2016 and 2020, inclusive. This amounted to US$24.5 billion (£19.7 billion) of investment across 66,388 research grants.

By country, the US provided 57.3% of the total cancer research funding awarded, with the US National Institute of Health being by far the biggest funder. Most of the world's biggest funders are transparent about their funding decisions, providing data on their grants. This allows for scrutiny around their portfolios and allows those who set funding priorities to better understand how to allocate limited resources for health research.

Among the major global health funders, Cancer Research UK is one of the few that does not provide data on funding at the individual award level. They rely on top-level summaries in annual reports and other infographics, which is insufficient for analyses such as ours. This makes it difficult to look into how the money was spent in detail.

Lung and thyroid cancers least funded

Our analysis compares the level of funding given to researching different types of cancers with the health burden of those types of cancer. This is important as it allows us to understand who is funding what in cancer research and to understand whether research gaps may exist.

We found that the cancer types receiving the most funding were breast (US$2.73 billion, 11.2% of the total) and haematological cancer (typically referring to leukaemia, US$2.3 billion, 9.4%).

In terms of the type of research, preclinical research (typically laboratory studies) received US$18 billion (73.5%). Pre-clinical studies are the earliest stage of research. The hope is that the findings from this stage of research will eventually "translate" into new or better treatments for cancer.

Preclinical studies are followed by testing in humans - clinical trials - which can take many years. If a drug or other treatment is proven to work, it then has to be approved by the drugs regulators, such as the US Food and Drug Administration or the European Medicines Agency.

The time taken from exploring preclinical science to a treatment used in practice can be up to 17 years. Most new products fail between the preclinical or clinical trial phases - more so in oncology (the study and diagnosis of tumours) than other areas of medicine.

Immuno-oncology is a relatively new therapeutic area that tries to develop treatments to enhance the body's immune system to fight cancer. In our analyses, immuno-oncology received 12% of the funding, reflecting the global desire to find new approaches to cancer treatments. However, such are the inequities in global health, that even if immuno-oncology and other new medicines make it into clinical practice, this will usually be in the richer countries. Poorer populations are unlikely to have access to the latest treatments.

We then looked at what investment 18 different types of cancer received and compared this against the number of deaths caused annually by each type of cancer. Our results suggest that lung cancer was particularly poorly funded.

We also reviewed a measure called "years lived with disability", which considers the effect of that disease on quality of life. Here, thyroid cancer came out as least-well funded. Both lung and thyroid cancers were judged to be the least well-funded cancer conditions overall, compared to their global burdens.

Cancer funding fell 45%

Our results show an average annual spend over the years 2016-19 of US$5.5 billion per year, with a 45% drop to US$2.9 billion in 2020. This might have been a natural fluctuation - cancer funding levels were declining to some extent - but it's possible the drop was caused by a diversion of funds into COVID research.

It's also likely that these drops in funding will mean less new knowledge coming through the cancer research pipeline. This will further affect patients at a time when the global burden is likely to increase, and may also drive further inequalities around access to cancer treatment and care.

Only 0.5% of cancer funding had a primary focus on lower-income countries, so it will not be easy for populations in poorer countries to benefit from new research findings. There was significant inequity in the COVID response, for example, with the distribution of vaccines during the height of the pandemic. There will be continuing consequences for wellbeing in other areas of health, with the worsening burden of cancer estimated to cause a drop in life expectancy.

From previous experience, it's fair to suggest that much of the preclinical research funded - by far the largest component of the portfolio - might not make it as far as being used in clinical care, and therefore only a small proportion of the current cancer research portfolio is going to be of direct benefit to patients at any point soon.

While some of this funding is, of course, essential for developing new treatments, the sheer volume of funding in this area means the overall portfolio may not be money well spent. While some of this type of research spending has driven innovative areas of medicine (such as immuno-oncology), there should be a new focus on prevention and also patient-focused research (such as the psychological and social effects of cancer).

There will be long-term consequences of the pandemic on other areas of health, including cancer. Our analysis showed the flow of funding into cancer research. This can help the global cancer research community better set future priorities. We must invest our limited global research resources as wisely as possible.

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Billions spent on cancer research globally - but is it money well spent?

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Lung and thyroid cancers are the least well-funded cancers compared to their global burdens.

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Information and Resources about for Cancer: Breast, Colon, Lung, Prostate, Skin

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Dedicated to helping people who face cancer. Learn about cancer research, patient services, early detection, treatment and education at cancer.org.