Cancer has been documented in human remains and medical texts for thousands of years, though doctors did not understand what caused it until the 1800s

Cancer is not a modern disease. Physicians found evidence of bone tumors in Egyptian mummies dating back to 1600 BCE, and ancient Greek and Roman doctors described cancerous growths in their medical writings. However, for most of human history, doctors had no idea what cancer actually was or why it happened. They could see the tumors and the damage they caused, but they could not explain the mechanism behind the disease. The real turning point came in the 1800s, when advances in microscopy and pathology allowed scientists to see cancer at the cellular level and begin to understand how it develops.

Key Takeaways

  • Ancient physicians documented cancer in medical texts and human remains, but did not understand its cause or nature.
  • The invention of the microscope in the 1600s made it possible to study cells, laying the groundwork for modern cancer science.
  • In the 1800s, pathologists discovered that cancer arises from abnormal cells and spreads through the body, establishing cancer as a cellular disease.
  • The 20th century brought targeted treatments based on understanding cancer's biology, including chemotherapy, radiation, and eventually drugs designed to attack specific cancer types.
  • Today's cancer research focuses on genetics and immunotherapy, building on centuries of accumulated knowledge about how the disease works.

What ancient doctors knew about cancer

The earliest written reference to cancer appears in the Edwin Smith Papyrus, an Egyptian medical text from around 1600 BCE. It describes eight cases of tumors or ulcers of the breast, and the physician's conclusion was blunt: there is no treatment. Ancient Greek physicians, including Hippocrates (around 460–370 BCE), used the word "karkinos"—meaning crab—to describe cancerous tumors, supposedly because the swollen veins around a tumor resembled a crab's legs. This term eventually became the Latin word "cancer," which is still used today.

Roman physician Galen (129–200 CE) theorized that cancer resulted from an excess of black bile, one of the four bodily humors that ancient medicine believed controlled health. This theory persisted for over 1,500 years. Physicians could observe that cancers grew, spread, and often killed their patients, but without microscopes or knowledge of cells, they could only guess at the underlying cause. Surgery was sometimes attempted, but outcomes were poor, and many doctors believed that cutting into a tumor would cause it to spread faster.

The microscope changes everything in the 1600s and 1700s

The invention of the microscope in the early 1600s opened an entirely new world of biological observation. Scientists like Antonie van Leeuwenhoek and Robert Hooke began examining tissues and discovering that all living things were made of tiny structures—cells. However, it took another century before scientists connected this cellular knowledge to cancer. Most physicians still believed in the humoral theory and did not yet see cancer as a disease of cells.

By the late 1700s, some physicians began to suspect that cancer might originate in the lymphatic system, which carries fluid throughout the body. This was closer to the truth, but still incomplete. The real breakthrough required better microscopes, better staining techniques to see cells clearly, and a willingness to abandon old theories in favor of what the microscope actually showed.

The 1800s: Cancer becomes a cellular disease

The turning point came in the mid-1800s, when German pathologist Rudolf Virchow and other scientists used improved microscopes to examine cancer tissue directly. In 1858, Virchow published his findings showing that cancer cells were abnormal versions of normal cells, and that cancer arose from the body's own tissues rather than from external poisons or humoral imbalances. This was revolutionary. Cancer was not a systemic disease of the whole body—it was a disease of individual cells that had gone wrong.

Around the same time, other researchers discovered that cancer cells could break away from a tumor and travel through the bloodstream or lymphatic system to other parts of the body, a process now called metastasis. This explained why cancer was so deadly and why it often returned even after surgery. By the end of the 1800s, the basic cellular nature of cancer was established, and doctors understood that the disease involved uncontrolled cell growth and spread.

The 20th century: From understanding to treatment

Once scientists understood that cancer was a cellular disease, they could begin to develop treatments based on that knowledge. In the early 1900s, radiation therapy emerged as doctors discovered that X-rays could kill cancer cells. Surgery improved as well, with better anesthesia and antiseptic techniques allowing surgeons to remove tumors more safely. However, these treatments were still crude—radiation damaged healthy tissue along with cancer cells, and surgery could not reach cancers deep inside the body.

The 1940s brought chemotherapy, drugs designed to poison cancer cells. The first chemotherapy drugs were discovered almost by accident when researchers noticed that mustard gas, a chemical weapon from World War I, could shrink tumors. Scientists refined this observation and developed the first intentional cancer drugs. By the 1950s and 1960s, combination chemotherapy—using multiple drugs together—showed promise against certain cancers, particularly childhood leukemia and lymphomas.

The latter half of the 20th century saw an explosion in cancer research. Scientists began to understand the genetic changes that drive cancer, discovering oncogenes (genes that promote cell growth) and tumor suppressors (genes that prevent uncontrolled growth). This knowledge led to targeted therapies—drugs designed to attack specific genetic mutations in cancer cells. By the 1990s and 2000s, drugs like Gleevec and Herceptin showed that targeting cancer's specific genetic flaws could be far more effective than poisoning all rapidly dividing cells.

Modern cancer research and immunotherapy

Today's cancer research builds on all of this accumulated knowledge. Scientists now understand that cancer is not one disease but hundreds of different diseases, each with its own genetic signature. This has led to personalized medicine approaches where treatment is tailored to the specific mutations in a patient's tumor. Immunotherapy—drugs that help the body's own immune system recognize and attack cancer cells—has emerged as a powerful new tool, approved for many cancer types over the past decade.

The journey from ancient observations of tumors to modern genetic and immunological treatments spans more than 3,500 years. Each era built on the discoveries of the previous one: ancient physicians documented the disease, Renaissance scientists developed the microscope, 19th-century pathologists revealed its cellular nature, and 20th and 21st-century researchers uncovered the genetic and molecular mechanisms that drive it. Understanding this history helps explain why cancer treatment has become so much more effective—and why research continues to evolve.

Frequently Asked Questions

Did people in ancient times get the same cancers we see today?

Yes, the same types of cancer existed in ancient times. Bone cancer, breast cancer, and other solid tumors appear in ancient medical texts and in skeletal remains. However, some cancers that are common today—like lung cancer from smoking—were rare or absent in ancient populations because the risk factors were different. Life expectancy was also much shorter, so people were less likely to live long enough to develop cancers that typically appear later in life.

Why did it take so long to understand what cancer really was?

Cancer is a disease of cells, and cells are invisible to the naked eye. Without microscopes, doctors could only see the external signs of cancer—swelling, ulcers, and tissue damage—but not the cellular changes causing them. Even after microscopes were invented, it took time to develop the staining techniques and magnification power needed to see cancer cells clearly. Additionally, old theories like the humoral model were deeply entrenched in medical education and practice.

When did doctors first successfully treat cancer?

Surgery has been used to remove tumors for centuries, with varying success. However, the first reliably effective cancer treatment was radiation therapy in the early 1900s. Chemotherapy in the 1940s marked another major milestone, particularly for blood cancers. Modern targeted therapies and immunotherapies, developed in the last 20 to 30 years, have dramatically improved survival rates for many cancer types.

Is cancer still being discovered today?

Doctors are not discovering new types of cancer, but they are constantly discovering new subtypes based on genetic differences. What was once classified as one type of cancer might now be understood as several distinct diseases with different mutations and different treatment approaches. This deeper understanding continues to improve how cancers are diagnosed and treated.