How does cancer spread through the body?

Metastasis: When cancer cells begin to travel through the body

Metastatic cancer starts in one part of the body and moves to another over time. This is known as metastasis. Such cancers are much more harmful since they attack multiple parts of the body, adapting new metabolic changes to suit the various environments found throughout a body.

Cancer is typically described by one of five stages

Stage 0 is in situ, meaning abnormal cells haven’t spread, while Stage 1 is further progressed but remains localized to the origin. Stage 2 and 3 show increasing tumor size and spread to nearby lymph nodes or tissues. Stage 4 indicates metastasis, meaning cancer has spread to distant organs.

How does cancer actually kill someone?

While the emotional and physical tolls of cancer are often clear, the innerworkings of how cancer kills can be confusing — and terrifying to discuss. Here, oncologists explain how cancer can progress.

Cancer is runaway growth of abnormal, mutated cells

Cancer cells have mutations in their DNA that allow uncontrolled growth and division, dodge usual mechanisms of cell death, and can often spread throughout the body. This is, in part, why the disease is so difficult to treat, with a wide variety of mechanisms and types that poses unique challenges.

The difference between standard cancer treatments and emerging immunotherapies

If you've ever wondered what the difference was between immunotherapy and chemotherapy, this short video takes you through the steps. Briefly, chemotherapy attacks cancer in tumor cells directly, while immunotherapy encourages your immune system to fight it. There's more to it than that, but this delightful two-and-a-half-minute video provides a good primer.

Explore interactive global maps of cancer prevalence

Cancer is a ubiquitous disease, with populations across the globe having incidence rates that reflect various risk factors. The Cancer Atlas lets users explore a comprehensive global overview of cancer statistics, including incidence, mortality, prevalence, and survival rates across various regions and Human Development Index categories.

Roughly 1 in 5 cancers are caused by viruses

About 20% of cancers are caused by viruses, with seven specific oncoviruses causing between 10% and 15% of cancers worldwide. These include human papillomavirus and hepatitis B and C viruses, which can lead to diseases such as cervical and liver cancer. Understanding the mechanisms of these viruses is crucial for prevention and treatment strategies.

Why don't we all have cancer?

The creation of a single cell produces 120,000 genetic mutations that can lead to cancer. This video investigates how our bodies proofread and autocorrect those mistakes.

Large animals like giraffes and elephants have evolved unique cancer defenses

One may expect the larger an animal is, the more likely it is to develop cancer—simply because there are more cells and more chances for a dangerous mutation. However, some large animals show cancer rates almost 10 times lower than humans—a phenomenon known as Peto's Paradox.

See how cholera spreads in a community

This animated video offers a comprehensive look at how cholera spreads. It makes clear why it's so difficult to stamp out this disease in communities around the world. It also details what steps can help control cholera.

How medical robots could cure cancer

Medical robots are on the verge of being able to be injected into the body, where they will be responsible for semi-autonomous behavior, such as detecting cancer cells and distributing medication. This six-minute video dives into the science of these nanorobots, which are smaller than blood cells. Applications of these nanobots could range from disease discovery and condition monitoring to tissue repair and artificial blood delivery.

Low cell division rates in heart cells make heart cancer particularly rare

The heart's location in the chest also offers protection from external cancer-causing factors. The disease affects about 3 in every 10,000 people, though most cases arise from metastasis from other body parts.

Watch what the Ebola virus does inside our cells and organs in order to spread and survive.

Explore the National Cancer Institute's archive on treatments

Cancer is a complex disease with many different types, each with its own pathology. The best treatment may depend on characteristics specific to each person—even if two people share the same type of cancer. No single overview of treatments exists, but this resource from the National Cancer Institute lets you explore different options, side effects, an A-to-Z library of cancer drugs, and much more.

Each part of the human body experiences aging differently

With global average life expectancy cresting at 73 years, understanding how the body ages is imperative to effective medical treatment and maintaining a desired quality of life. This 13-minute video dives into how the body and its organs age "from head to toe."

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

Searching for the history of cancer in ancient human bones

Nestled under archaeology lies bioarchaeology, which involves the study of bones, human or animal. This subfield recently birthed another field of study: paleo-oncology. Paleo-oncology looks for cancer and related biomarkers in bioarchaeological remains. This TED article explains how this nascent multidisciplinary field challenges the idea that cancer is modern.

Watch what the Ebola virus does inside the body in order to spread and survive

Once infected, the virus targets the body's immune cells, spreading the infection throughout the body. Patients exhibit severe flu-like symptoms. Ebola then targets the liver, which produces proteins that help blood clot, and the adrenal glands, which control blood pressure. The immune system may overreact to the viral invasion, releasing a cytokine storm that can result in shock, multiple organ failure, and death.

Theoretically, you could lose a bunch of your organs and still survive

If surgeons removed organs including one of your lungs, a kidney, your spleen, appendix, tonsils, part of your liver, and even some of your reproductive organs you could still survive. Watch this animated video which dives into the organs you could conceivably live without.

How does food move through the body?

Food passes through the digestive system via muscle movement known as peristalsis, during which a rippling contraction slowly pushes content through tubular organs, such as the esophagus and intestines. This is similar to what happens when one squeezes a tube of toothpaste, contracting the tube behind the content and forcing the tube in front of the content to expand, allowing the content to move forward.

An interactive dive into the immune system

Our bodies are equipped with an incredible system able to fight off invasive pathogens to protect us from illness. The complicated system includes lymph nodes, the spleen, bone marrow, and even the tonsils. But this same system can turn against itself, a condition known as autoimmune disorders. Follow along with this thorough, engaging explainer on the human body's defense system.

Fungi make people sick when they invade and survive in otherwise healthy human tissue

We breathe in airborne spores frequently, but they often don't make us sick. This video details how certain concerning fungal changes can occur and discusses the role of mycologists—scientists who study fungi—in helping to improve human health.

See where and how many microplastics are in the average human body

This diagram maps the extent to which microplastics have been found across human organ systems, tissues, and fluids. Beyond the locations shown, microplastics have also been found in the stomach, brain, and sex organs.

You can sign up to donate your body to science

It's a separate process to donate your body for medical research; you usually must contact a whole-body donation program directly. Bodies can be donated for medical research, for forensic analysis research, or for medical students to work with as they learn anatomy and surgery, among other purposes. Learn more about numerous accredited organizations that provide human bodies, organs, and tissues to medical researchers and students.

Different types of malware are categorized by how they spread or operate

Computer viruses require user interaction to execute a file and spread, whereas worms can self-replicate across systems without human intervention. Ransomware locks systems until a key is provided, spyware tracks and reports user activity to a third party, and trojans disguise various types of malware as legitimate software.

Every organ in a mother's body changes during pregnancy

There's limited real estate inside a mother's body; as the uterus grows both up and out, it shifts other organs to make space. A pregnant woman's body produces hormones to loosen muscles to allow for this expansion. Pregnancy also triggers other changes, including faster breathing to compensate for decreased diaphragm range.

Resistant infections are no longer isolated and can spread worldwide

What does the rise of antibiotic resistance mean in practical terms? Maryn McKenna is a journalist at the forefront of covering antibiotic resistance since 2007. In this TED talk, McKenna lays out the very real consequences of antibiotic resistance—and what needs to be done to address the problem.

Tattoos remain visible on your skin thanks to immune cells called macrophages

Louisiana's 'Cancer Alley' is infamous for having some of the highest industrial pollution, toxic air emissions, and cancer risks in the US.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

Firework or sparkler burns, even if they cover a relatively small area of skin, can significantly affect our range of motion.

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

Watch how deep-sea mining equipment collects and processes polymetallic nodules—metal-rich, potato-shaped rocks—from the ocean floor and creates environmentally damaging plumes of sediments.

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Learn how to read a prospectus, the juicy document that any company must file with the SEC before going public.

After the Boston Tea Party, colonists switched to coffee, which became the main morning drink for revolutionaries.