There are more than 200 types of cancer, but they fall into a few main categories

Cancer is not one disease. Doctors have identified more than 200 distinct types, each starting in a different cell type or organ and behaving differently under treatment. The number keeps growing as medical technology improves and researchers identify subtypes within what were once thought to be single cancers.

The main categories are carcinomas (cancers of skin, lung, breast, and digestive organs), sarcomas (cancers of bone, muscle, and connective tissue), leukemias (cancers of blood cells), lymphomas (cancers of immune system cells), and melanomas (cancers of pigment cells). Within each category, there are dozens of subtypes based on where the cancer starts and what kind of cell is affected.

What matters most for treatment is not the total number of cancer types, but which specific type a person has. Two people with "lung cancer" might have completely different diseases at the cellular level, requiring different treatment approaches. This is why doctors do extensive testing to identify not just the organ where cancer started, but the exact cell type and genetic changes involved.

Key Takeaways

  • More than 200 types of cancer exist, grouped into five main categories based on the kind of cell where cancer starts.
  • Carcinomas are the most common type and begin in the skin or lining of organs like the lungs, breast, and digestive tract.
  • The specific type of cancer matters more than the total number of types because treatment depends on which cells are affected and what genetic changes are present.
  • Doctors continue to identify new subtypes as genetic testing becomes more detailed, so the number of recognized cancer types increases over time.
  • Two cancers in the same organ can be different diseases at the cellular level and may respond to completely different treatments.

The five main cancer categories and where they start

Carcinomas are cancers that begin in the cells lining organs or covering the body. They are the most common type, making up about 80 to 90 percent of all cancers. Breast cancer, lung cancer, colorectal cancer, and skin cancer are all carcinomas. They can start in almost any organ—the pancreas, liver, stomach, prostate, ovaries, and thyroid all develop carcinomas.

Sarcomas start in bone, muscle, fat, or other connective tissue. They are much rarer than carcinomas, making up only about 1 percent of all cancers. Osteosarcoma (bone cancer) and rhabdomyosarcoma (muscle cancer) are examples. Because sarcomas are uncommon, they are often diagnosed later than carcinomas.

Leukemias are cancers of blood cells. They start in the bone marrow, where blood cells are made, and spread through the bloodstream rather than forming solid tumors. Acute lymphoblastic leukemia (ALL) and chronic myeloid leukemia (CML) are two examples. Leukemias are more common in children than in adults, though adults can develop them at any age.

Lymphomas are cancers of lymphocytes, a type of white blood cell that fights infection. They start in the lymph nodes or spleen and spread through the lymphatic system. Hodgkin lymphoma and non-Hodgkin lymphoma are the two main types, with non-Hodgkin being more common. Lymphomas can develop in almost any part of the body where lymph tissue exists.

Melanomas are cancers of melanocytes, the cells that produce skin pigment. They usually start on the skin but can also begin in the eye or other parts of the body. Melanoma is less common than other skin cancers but more likely to spread to other organs if not caught early.

Why doctors divide cancers into subtypes

Within each main category, there are many subtypes. Breast cancer alone has at least a dozen recognized subtypes based on whether the cancer cells have receptors for hormones or growth factors. Lung cancer divides into small cell lung cancer and non-small cell lung cancer, and non-small cell further divides based on which cells are affected—adenocarcinoma, squamous cell carcinoma, or large cell carcinoma.

These divisions matter because they predict how fast the cancer will grow, whether it will respond to certain drugs, and what the likely outcome is. A person with hormone receptor-positive breast cancer may respond well to hormone-blocking drugs, while someone with triple-negative breast cancer will not. Two people with the same organ affected can need completely different treatment plans.

Genetic testing has made these divisions more precise. Doctors now look for specific mutations—changes in the DNA of cancer cells—that determine which drugs will work. A lung cancer patient whose tumor has an EGFR mutation might respond to a targeted drug that would not help someone whose tumor has a different mutation. This is why genetic testing of the tumor itself has become standard practice for many cancer types.

How the number of cancer types continues to grow

The count of "200 types" is not fixed. As technology improves, researchers identify subtypes that were previously grouped together. What was once called "non-small cell lung cancer" is now recognized as several distinct diseases based on genetic changes. The same is happening with other cancers as whole-genome sequencing becomes faster and cheaper.

Medical organizations like the World Health Organization update their classification of cancers every few years as new information emerges. The most recent major update recognized new subtypes of brain tumors, blood cancers, and soft tissue sarcomas. This does not mean new cancers are appearing—it means doctors are getting better at distinguishing between cancers that look similar under a microscope but behave differently.

This ongoing refinement is good news for patients because more precise classification leads to more targeted treatment. A cancer that was once treated with one standard approach might now be treated with a drug designed specifically for its genetic profile. The more types doctors recognize, the more treatment options become possible.

The most common cancers and their subtypes

Breast cancer is the most common cancer in women and has at least 12 recognized subtypes based on hormone receptor status and HER2 status. Lung cancer is the second most common overall and divides into small cell and non-small cell types, with non-small cell further divided into adenocarcinoma, squamous cell, and large cell. Colorectal cancer starts in the colon or rectum and can be divided into subtypes based on location and genetic mutations.

Prostate cancer is the most common cancer in men and ranges from slow-growing to aggressive based on genetic markers and how abnormal the cells look under a microscope. Melanoma and non-melanoma skin cancers (basal cell and squamous cell) are extremely common but often have better outcomes than internal cancers because they are visible and caught early. Pancreatic cancer, ovarian cancer, and liver cancer are less common but tend to be diagnosed at later stages, which affects treatment options.

How doctors determine which type of cancer a person has

Diagnosis starts with a biopsy—a small sample of tissue taken from the tumor. A pathologist looks at the cells under a microscope to determine what type they are and how abnormal they appear. This is called the grade and is one of the first pieces of information that guides treatment decisions.

Next, doctors usually order imaging tests like CT scans or MRI to see how large the tumor is and whether it has spread. Blood tests may show markers that indicate a specific cancer type. For many cancers, genetic testing of the tumor cells is now standard—this reveals mutations that determine which drugs are most likely to work.

The combination of where the cancer started, what the cells look like, how fast they are dividing, and what genetic changes are present all together determine the specific type and subtype. This information goes into a pathology report that becomes the foundation for treatment planning. Two people diagnosed with "cancer" may actually have very different diseases based on these details.

Frequently Asked Questions

Is cancer the same disease in different parts of the body?

No. A cancer that starts in the breast is a different disease from a cancer that starts in the lung, even if cells from the breast cancer spread to the lung. The original location and cell type determine how the cancer behaves and what treatment works. Doctors classify it by where it started, not where it has spread.

Why do some cancers have the same name but different treatments?

Because genetic testing has revealed that cancers with the same name can have different mutations. Two people with lung cancer might receive different drugs based on whether their tumor has an EGFR mutation, an ALK mutation, or neither. The name describes the location; the genetic profile determines the treatment.

Can a person have more than one type of cancer at the same time?

Yes, though it is uncommon. A person can develop a second cancer in a different organ while being treated for the first, or years after the first cancer is gone. Each cancer is treated separately based on its own type and stage. The risk of developing a second cancer is higher for some people based on genetics or previous treatment.

Does the number of cancer types affect my treatment options?

The specific type and subtype of your cancer directly affects your treatment. More precise classification means more targeted drugs are available. Your doctor will order tests to identify your cancer's exact type and genetic profile, and that information determines which treatments are most likely to work for you.

Are new cancer types being discovered?

Not new cancers appearing in the world, but new subtypes being recognized as technology improves. Genetic sequencing is revealing that cancers previously thought to be one type are actually several distinct diseases. This leads to more treatment options because drugs can be developed for specific genetic profiles rather than broad cancer categories.