What is metastatic cancer?
Metastatic cancer is a cancer that has spread from the part of the body where it started (the primary site) to other parts of the body. When cancer cells break away from a tumor, they can travel to other areas of the body through the bloodstream or the lymph system (which contains a collection of vessels that carry fluid and immune system cells).
This image shows some parts of the lymph system, like lymph nodes and lymph vessels, as well as organs and tissues that contain many lymphocytes (immune cells)
If the cells travel through the lymph system, they may end up in nearby lymph nodes (small, bean-sized collections of immune cells) or they may spread to other organs. More often, cancer cells that break off from the main tumor travel through the bloodstream. Once in the blood, they can go to any part of the body. Many of these cells die, but some may settle in a new area, begin to grow, and form new tumors. This spread of cancer to a new part of the body is called metastasis.
Cancer cells have to go through several steps to spread to new parts of the body:.
- They have to be able to break away from the original tumor and enter the bloodstream or lymph system, which can carry them to another part of the body.
- They need to attach to the wall of a blood or lymph vessel and move through it into a new organ.
- They need to be able to grow and thrive in their new location.
- They need to be able to avoid attacks from the body’s immune system.
Going through all these steps means the cells that start new tumors may no longer be exactly the same as the ones in the tumor they started in. This may make them harder to treat.
Even when cancer has spread to a new area, it’s still named after the part of the body where it started. Treatment is also based on where the cancer started. For example, if prostate cancer spreads to the bones, it’s still prostate cancer (not bone cancer), and the doctor will recommend treatments that have been shown to help against metastatic prostate cancer. Likewise, breast cancer that has spread to the lungs is still breast cancer, not lung cancer, and is treated as metastatic breast cancer.
Sometimes the metastatic tumors have already begun to grow when the cancer is first found and diagnosed. And in some cases, a metastasis may be found before the original (primary) tumor is found. If a cancer has already spread to many places when it’s found, it may be very hard to figure out where it started. If this happens the cancer is called cancer of unknown primary. This is discussed in Cancer - Unknown Primary.
Why cancer cells tend to spread to certain parts of the body
Where a cancer starts often plays a role in where it will spread. Most cancer cells that break free from the original tumor are carried in the blood or lymph until they get trapped in the next “downstream” organ or set of lymph nodes. Once the cells are there, they can start new tumors. This explains why breast cancer often spreads to underarm lymph nodes, but rarely to lymph nodes in the groin. Likewise, there are many cancers that commonly spread to the lungs. This is because the heart pumps blood from the rest of the body through the lungs’ blood vessels before sending it elsewhere. The liver is a common site of spread for cancer cells that start in the colon because blood from the intestines flows into the liver.
Cancer cells often break away from the main (primary) tumor and travel through the blood and/or lymph system, but they don’t always settle in and start new tumors. Most of the time, the cells that broke away die. When cancer does spread to other organs and start to form new tumors, it’s because of certain genetic changes in the cells that scientists are now starting to understand. Someday, doctors may be able to tell if a person’s cancer is the type that will spread to other organs by looking for these genetic changes. Research is also focusing on treatments that block or target these genetic changes so the cancer cells can’t spread and grow.
Sometimes the patterns of spread cannot be explained by where things are in the body. Some cancer cells are able to find and invade certain sites far away from where they started. For example, advanced prostate cancer often moves into the bones before spreading to other organs. This “homing” pattern may be caused by substances on the cancer cell surfaces that stick to cells in certain organs.
Which cancers spread where?
This is a brief description of where certain cancers are most likely to spread. It’s not a list of every place where a cancer could spread. For more details on these cancers, see our information on the specific cancer site.
Bladder cancer tends to stay in the same area (the pelvis) and grow into nearby tissues such as the pelvic wall. It can also spread to the lungs, liver, and bone.
Brain tumors rarely spread outside the brain. They mainly grow within the brain and sometimes into the spinal cord.
Breast cancer most commonly spreads to the bones, but also can spread to the liver, lungs, and brain. As the cancer progresses, it may affect any organ. It can also spread to the skin of the chest (near where the cancer started).
Cancer of the cervix tends to grow near where it started, into the vagina and uterus and then other parts of the pelvis, such as the rectum and bladder. It can also grow into the bones and nerves of the spine, and spread to the liver, lungs, and bones.
Colon and rectum
The most common sites for colon or rectal cancer spread are the liver and lungs. These cancers may also spread to nearly any other organ, including the bones and brain.
Rectal cancer can also spread within in the pelvis, where the cancer started. This can be painful because it often grows into nerves and bones in this area.
Esophageal cancer mostly grows near where it started (in the chest and belly). As it progresses, it may grow into nearby organs or major blood vessels, which can make it hard to treat.
Kidney (renal) cancer can grow where it started and invade nearby tissues. It can grow from the kidney into the large vein that drains the blood from the kidney (the renal vein). From there it can grow into a large vein that empties into the heart (the inferior vena cava). It can also grow from the kidney into the adrenal gland, which sits on top of the kidney. When it spreads, the lungs and bones are the most common sites.
Because they are already in the blood, leukemias can be considered to have spread throughout the body when they are diagnosed. They can progress by filling the bone marrow with leukemia cells. The normal bone marrow is replaced and cannot make new blood cells.
Some leukemias may spread outside the blood and into the fluid that surrounds the brain and spinal cord. Tumors made up of leukemia cells can also occur in the skin or in other parts of the body, but this is not common. In some types of leukemia, the cancer cells collect in the spleen, causing it to become large. Less often, leukemia cells settle in the liver, causing it to enlarge. In one type of leukemia, the cells deposit in the gums, so that they become red and swollen.
Liver cancer doesn’t often spread outside the liver. It tends to grow throughout the liver as it becomes advanced. If it does spread, it’s most often to the lungs or bones.
Lung cancer can spread to almost any organ of the body, but most often it will spread to the adrenal glands, liver, bones, or brain. It can also spread to the other lung.
Lymphoma can affect any part of the body. While most start in the lymph nodes, spleen, and/or bone marrow, some start in lymph tissue in the stomach, intestines, or even the eye socket. Lymphomas can spread within the lymph system to distant parts of the body. Less often, they spread outside the lymph system to other organs, such as the lungs, liver, or bone. Lymphomas can affect the brain and spinal cord, either initially (called primary central nervous system lymphoma) or as spread to the fluid and tissues (the meninges) surrounding the brain and spinal cord. This is called lymphomatous meningitis.
Melanoma can spread anywhere in the body. It first tends to go to lymph nodes near where it started, but then can spread to the brain, lungs, liver, and bones. It can also spread to other areas of skin.
Mouth and throat
Multiple myeloma can cause tumors called plasmacytomas. These tumors can spread to the bones anywhere in the body, but they rarely spread to other organs.
Ovarian cancer most often spreads to the lining of the abdomen (belly) and pelvis (this lining is called the peritoneum), the omentum (a layer of connective tissue that drapes the abdominal cavity like an apron), and organs in the pelvis and belly. It can cause a build-up of fluid and swelling in the abdomen. It can also spread to the outer lining of the lungs and cause fluid to build up there. As it becomes more advanced, it may spread to the lung and liver, or, rarely, to the brain or skin.
Pancreatic cancer mainly stays in the abdomen (belly). It tends to grow into nearby tissues and may spread to the liver or other nearby organs. It can also spread to the lungs.
Advanced prostate cancer most often goes to the bones. Much less often, it will spread to other organs, including the lungs and liver.
Stomach (gastric) cancer tends to spread to nearby tissues and stay within the abdomen (belly). It may also spread to the liver or distant lymph nodes. Spread to the lungs, bones, and brain is less common.
Cancer that starts in the uterus can grow into the vagina as well as nearby tissues in the pelvis. It also commonly spreads to the peritoneum (the lining of the abdominal cavity and pelvis) and the omentum (a layer of connective tissue that drapes the abdominal cavity like an apron). Other sites of cancer spread include the liver, lungs, and, less often, bones.
- Advanced Cancer
- What is advanced cancer?
- What is metastatic cancer?
- Can advanced or metastatic cancer be prevented?
- How is advanced cancer found?
- How is advanced cancer treated?
- Surgery for advanced cancer
- Ablative techniques for advanced cancer
- Radiation therapy for advanced cancer
- Drug treatment for advanced cancer
- Clinical trials
- Complementary and alternative therapies for advanced cancer
- Managing symptoms of advanced cancer, by location
- Managing general symptoms of advanced cancer
- What should you ask your doctor about advanced cancer?
- Coping with advanced cancer
- Sources of support
- Choices for palliative care
- Advance directives
- Additional resources for advanced cancer
- References: Advanced cancer