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Metastatic Cancer: Questions and Answers

1. What is cancer?

Cancer is a group of many related diseases. All cancers begin in cells, the building 

blocks that make up tissues. Cancer that arises from organs and solid tissues is called a 

solid tumor. Cancer that begins in blood cells is called leukemia, multiple myeloma, or 

lymphoma. 

Normally, cells grow and divide to form new cells as the body needs them. When cells 

grow old and die, new cells take their place. Sometimes this orderly process goes wrong. 

New cells form when the body does not need them, and old cells do not die when they 

should. 

The extra cells form a mass of tissue, called a growth or tumor. Tumors can be either 

benign (not cancerous) or malignant (cancerous). Benign tumors do not spread to other 

parts of the body, and they are rarely a threat to life. Malignant tumors can spread 

(metastasize) and may be life threatening. 

Key Points 

• Cancer occurs when cells become abnormal and grow without control (see 

Question 1). 

• The place where the cancer started is called the primary cancer or the primary 

tumor (see Question 2). 

• Metastatic cancer occurs when cancer cells spread from the place where the 

cancer started to other parts of the body (see Question 3). 

• When cancer spreads, the metastatic cancer has the same type of cells and 

the same name as the primary tumor (see Question 3). 

• The most common sites of metastasis are the lungs, bones, liver, and brain 

(see Question 4). 

• Treatment for metastatic cancer usually depends on the type of cancer as well 

as the size and location of the metastasis (see Question 8). 
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2. What is primary cancer? 

Cancer can begin in any organ or tissue of the body. The original tumor is called the 

primary cancer or primary tumor. It is usually named for the part of the body or the type 

of cell in which it begins. 

3. What is metastasis, and how does it happen? 

Metastasis means the spread of cancer. Cancer cells can break away from a primary 

tumor and enter the bloodstream or lymphatic system (the system that produces, stores, 

and carries the cells that fight infections). That is how cancer cells spread to other parts 

of the body. 

When cancer cells spread and form a new tumor in a different organ, the new tumor is a 

metastatic tumor. The cells in the metastatic tumor come from the original tumor. This 

means, for example, that if breast cancer spreads to the lungs, the metastatic tumor in the 

lung is made up of cancerous breast cells (not lung cells). In this case, the disease in the 

lungs is metastatic breast cancer (not lung cancer). Under a microscope, metastatic breast 

cancer cells generally look the same as the cancer cells in the breast. 

4. Where does cancer spread? 

Cancer cells can spread to almost any part of the body. Cancer cells frequently spread to 

lymph nodes (rounded masses of lymphatic tissue) near the primary tumor (regional 

lymph nodes). This is called lymph node involvement or regional disease. Cancer that 

spreads to other organs or to lymph nodes far from the primary tumor is called metastatic 

disease. Doctors sometimes also call this distant disease. 

The most common sites of metastasis from solid tumors are the lungs, bones, liver, and 

brain. Some cancers tend to spread to certain parts of the body. For example, lung 

cancer often metastasizes to the brain or bones, and colon cancer frequently spreads to 

the liver. Prostate cancer tends to spread to the bones. Breast cancer commonly spreads 

to the bones, lungs, liver, or brain. However, each of these cancers can spread to other 

parts of the body as well. 

Because blood cells travel throughout the body, leukemia, multiple myeloma, and 

lymphoma cells are usually not localized when the cancer is diagnosed. Tumor cells may 

be found in the blood, several lymph nodes, or other parts of the body such as the liver or 

bones. This type of spread is not referred to as metastasis. 

5. Are there symptoms of metastatic cancer? 

Some people with metastatic cancer do not have symptoms. Their metastases are found 

by x-rays and other tests performed for other reasons. 
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When symptoms of metastatic cancer occur, the type and frequency of the symptoms will 

depend on the size and location of the metastasis. For example, cancer that spreads to the 

bones is likely to cause pain and can lead to bone fractures. Cancer that spreads to the 

brain can cause a variety of symptoms, including headaches, seizures, and unsteadiness. 

Shortness of breath may be a sign of lung involvement. Abdominal swelling or jaundice 

(yellowing of the skin) can indicate that cancer has spread to the liver. 

Sometimes a person’s primary cancer is discovered only after the metastatic tumor causes 

symptoms. For example, a man whose prostate cancer has spread to the bones in his 

pelvis may have lower back pain (caused by the cancer in his bones) before he 

experiences any symptoms from the primary tumor in his prostate. 

6. How does a doctor know whether a cancer is a primary or a metastatic tumor? 

To determine whether a tumor is primary or metastatic, a pathologist examines a sample 

of the tumor under a microscope. In general, cancer cells look like abnormal versions of 

cells in the tissue where the cancer began. Using specialized diagnostic tests, a 

pathologist is often able to tell where the cancer cells came from. Markers or antigens 

found in or on the cancer cells can indicate the primary site of the cancer. 

Metastatic cancers may be found before or at the same time as the primary tumor, or 

months or years later. When a new tumor is found in a patient who has been treated for 

cancer in the past, it is more often a metastasis than another primary tumor. 

7. Is it possible to have a metastatic tumor without having a primary cancer? 

No. A metastatic tumor always starts from cancer cells in another part of the body. 

In most cases, when a metastatic tumor is found first, the primary tumor can be found. 

The search for the primary tumor may involve lab tests, x-rays, and other procedures. 

However, in a small number of cases, a metastatic tumor is diagnosed but the primary 

tumor cannot be found, in spite of extensive tests. The pathologist knows the tumor is 

metastatic because the cells are not like those in the organ or tissue in which the tumor is 

found. Doctors refer to the primary tumor as unknown or occult (hidden), and the patient 

is said to have cancer of unknown primary origin (CUP). Because diagnostic techniques 

are constantly improving, the number of cases of CUP is going down. More information 

about CUP can be found in the National Cancer Institute (NCI) fact sheet Cancer of 

Unknown Primary Origin, which is available at 

http://www.cancer.gov/cancertopics/factsheet/Sites-Types/unknownprimary on the 

Internet. 

8. What treatments are used for metastatic cancer? 

When cancer has metastasized, it may be treated with chemotherapy, radiation therapy, 

biological therapy, hormone therapy, surgery, cryosurgery, or a combination of these. 

The choice of treatment generally depends on the type of primary cancer, the size and 
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location of the metastasis, the patient’s age and general health, and the types of 

treatments the patient has had in the past. In patients with CUP, it is possible to treat the 

disease even though the primary tumor has not been located. The goal of treatment may 

be to control the cancer, or to relieve symptoms or side effects of treatment. 

9. Are new treatments for metastatic cancer being developed? 

Yes, many new cancer treatments are under study. To develop new treatments, the NCI 

sponsors clinical trials (research studies) with cancer patients in many hospitals, 

universities, medical schools, and cancer centers around the country. Clinical trials are a 

critical step in the improvement of treatment. Before any new treatment can be 

recommended for general use, doctors conduct studies to find out whether the treatment 

is both safe for patients and effective against the disease. The results of such studies have 

led to progress not only in the treatment of cancer, but in the detection, diagnosis, and 

prevention of the disease as well. Patients interested in taking part in a clinical trial 

should talk with their doctor. 

# # # 

Related Resources

Publications (available at http://www.cancer.gov/publications) 

• National Cancer Institute Fact Sheet 5.32, Staging: Questions and Answers

• National Cancer Institute Fact Sheet 6.7, Cancer: Questions and Answers

• National Cancer Institute Fact Sheet 6.19, Cancer of Unknown Primary Origin

• What You Need To Know AboutTM Cancer

National Cancer Institute (NCI) Resources

Cancer Information Service (toll-free)

 Telephone: 1–800–4–CANCER (1–800–422–6237) 

 TTY: 1–800–332–8615 

Online 

NCI’s Web site: http://www.cancer.gov 

LiveHelp, NCI’s live online assistance: 

https://cissecure.nci.nih.gov/livehelp/welcome.asp

 

This fact sheet was reviewed on 9/1/04