"After reading this I lamented, for we have a long way to go in Africa. Even ethnic minorities in developed countries, still don’t take Breast cancer seriously."
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 tumour, 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).
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 tumour 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 tumours. 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 tumour 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 tumours may no longer be exactly the same as the ones in the tumour 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 tumours 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) tumour 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.
Where a cancer starts often plays a role in where it will spread. Most cancer cells that break free from the original tumour 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 tumours. 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) tumour and travel through the blood and/or lymph system, but they don’t always settle in and start new tumours. Most of the time, the cells that broke away die. When cancer does spread to other organs and start to form new tumours, 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.
(Source material American Cancer Society)