There are more than 200 types of cancer, and they are named by where they start

Cancer is not one disease. Doctors have identified more than 200 distinct types, each starting in a different cell or tissue. A cancer is named for the organ or cell type where it begins — lung cancer starts in the lungs, breast cancer in breast tissue, colon cancer in the colon. The same cancer type can behave differently from person to person, and treatment that works for one type often does not work for another.

The number keeps growing as medical technology improves and doctors recognize cancers that were once grouped together as separate conditions. What matters for you is not memorizing all 200 types, but understanding that your specific cancer has its own biology, its own treatment options, and its own prognosis — and that knowing which type you have is the first step toward understanding what comes next.

Key Takeaways

  • Cancers are named by the organ or tissue where they start, so the same cancer type behaves the same way regardless of where it spreads.
  • The four most common types in the United States are breast, lung, prostate, and colorectal cancer, which together account for roughly half of all new diagnoses.
  • Rare cancers exist but are defined as those affecting fewer than 15 people per 100,000 per year, and some are so uncommon that few hospitals have treated them.
  • Two people with the same cancer type can have different subtypes based on genetic mutations, which changes which treatments will work.
  • Your pathology report names your specific cancer type and subtype, and this information determines what treatment options your doctor will discuss.

The most common cancers in the United States

Breast cancer is the most frequently diagnosed cancer in women, with roughly 300,000 new cases per year. Lung cancer is the second most common overall and the leading cause of cancer death. Prostate cancer is the most common cancer in men. Colorectal cancer affects both men and women and is the third most common type.

These four cancers account for about half of all new cancer diagnoses. That concentration means most hospitals have treatment programs for them, most oncologists have deep experience with them, and most clinical trials test new drugs against them. If you are diagnosed with one of these types, you will have more treatment options and more specialists to choose from than someone with a rarer cancer.

Beyond these four, the next tier includes melanoma (skin cancer), non-Hodgkin lymphoma (blood cancer), thyroid cancer, pancreatic cancer, and ovarian cancer. Each of these has its own treatment pathways and its own survival rates. The remaining 190-plus types are less common but still occur regularly enough that major cancer centers see them.

Rare cancers and why they matter

A cancer is considered rare if it affects fewer than 15 people per 100,000 people per year in the United States. This includes cancers like mesothelioma (linked to asbestos exposure), cholangiocarcinoma (bile duct cancer), and various sarcomas (cancers of bone, muscle, or connective tissue). Some rare cancers are so uncommon that only a handful of hospitals in the country have treated more than a few cases.

If you are diagnosed with a rare cancer, finding a specialist becomes more difficult. Your local hospital may not have an oncologist who regularly treats your type. You may need to travel to a major cancer center or seek a second opinion from a specialist who focuses on your specific cancer. Organizations like the National Organization for Rare Disorders (NORD) and disease-specific foundations can connect you with specialists and other patients with your diagnosis.

How cancers are classified by cell type

Beyond location, cancers are also sorted by the type of cell they come from. Carcinomas start in cells that line organs or glands — breast cancer, lung cancer, and colon cancer are all carcinomas. Sarcomas start in bone, muscle, or connective tissue. Leukemias start in blood-forming cells in the bone marrow. Lymphomas start in immune cells in the lymph nodes and spleen.

This cell-type classification matters because it affects how the cancer spreads and which treatments work. A sarcoma will not respond to drugs designed for carcinomas. A leukemia is treated very differently from a solid tumor. Your pathology report will tell you both where your cancer started and what type of cell it came from, and your oncologist will use both pieces of information to plan your treatment.

Subtypes and genetic mutations change treatment options

Two people can have breast cancer, but their cancers may be different at the molecular level. Breast cancer is divided into subtypes based on whether the cancer cells have receptors for hormones (estrogen and progesterone) and whether they produce extra copies of a protein called HER2. A hormone-receptor-positive cancer responds to hormone-blocking drugs. A HER2-positive cancer responds to drugs that target that protein. A triple-negative cancer (negative for all three markers) requires different treatment entirely.

The same pattern holds for other cancers. Lung cancer is divided into types based on genetic mutations like EGFR, ALK, and KRAS. Colon cancer subtypes are identified by microsatellite instability and other genetic markers. Your pathology report and genetic testing will reveal your cancer's subtype, and this information narrows down which drugs are most likely to work for you. Two people with the same cancer type but different subtypes may receive completely different treatment plans.

How doctors determine your cancer type

Your cancer type is determined through a biopsy — a sample of tissue taken from the tumor and examined under a microscope by a pathologist. The pathologist looks at the cells' shape, size, and behavior, and compares them to known cancer types. Modern pathology also includes genetic testing, which identifies specific mutations in your cancer cells. This genetic information helps your oncologist choose targeted drugs that work against those specific mutations.

The result is your pathology report, a document that names your cancer type, describes how abnormal the cells look (called the grade), and lists any genetic mutations found. This report is the foundation of your treatment plan. You should ask for a copy and bring it to all your appointments. If you want a second opinion, you will send this report to the other oncologist so they can review it.

What happens when a cancer type is very rare or newly recognized

Occasionally a pathologist encounters cells that do not fit neatly into an existing category. This can happen when a cancer is extremely rare, when it is a newly recognized subtype, or when it has unusual genetic features. In these cases, the pathologist may send the sample to a specialized laboratory or to another pathologist for review. This process takes longer but ensures you get an accurate diagnosis.

If your cancer is newly recognized or very rare, your oncologist may recommend genetic testing through a specialized lab, or may suggest you be seen at a major cancer center where specialists have experience with unusual cases. Some rare cancers are treated through clinical trials because standard treatments have not been established. Your doctor can search ClinicalTrials.gov to find trials that match your specific cancer type and genetic profile.

Frequently Asked Questions

Does it matter what my cancer is called if the treatment is the same?

Yes. Cancer names are based on biology, not just location. Two cancers with different names almost always respond to different drugs. Even if two cancers are treated in the same organ, they may require completely different approaches. Your cancer's name tells your oncologist which drugs to try first and which side effects to watch for.

Can a cancer change types or turn into a different cancer?

A cancer does not change into a different type. However, a cancer can spread to other organs, and the spread is still named for where it started — breast cancer that spreads to the lungs is still called breast cancer, not lung cancer. Rarely, a person can develop two separate cancers at different times, but these are separate diagnoses, not a transformation.

What if my pathology report says my cancer is a subtype I have never heard of?

Ask your oncologist to explain what the subtype means for your treatment. Subtypes exist because they respond differently to drugs, so knowing your subtype helps your doctor choose the most effective treatment. If the subtype is very rare, your oncologist may recommend genetic counseling or a consultation with a specialist who focuses on that specific subtype.

Are there cancers that do not fit into the 200-type system?

The 200-plus types cover the vast majority of cancers. Occasionally a tumor is so unusual that pathologists must do extensive testing to classify it, but it will eventually be placed into an existing category or recognized as a new subtype. This process is normal and does not delay treatment — your oncologist can often start therapy while final classification is underway.

How do I find a specialist if I have a rare cancer?

Start by asking your oncologist for a referral to a specialist or major cancer center with experience in your cancer type. You can also search the National Cancer Institute's physician database, contact disease-specific foundations (many rare cancers have their own), or call NORD for guidance. Some rare cancers have patient advocacy groups that maintain lists of experienced doctors.