BONE METASTASIS

When cancer spreads from the part of the body where it started (its primary site) to other parts of the body it’s called metastasis. Metastasis can happen when cells break away from a cancer tumor and travel through the bloodstream or through lymph vessels to other parts of the body. (Lymph vessels are much like blood vessels, except they carry a clear fluid called lymph back toward the heart.) Cancer cells that travel through the blood or lymph vessels can spread to other organs or tissues in distant parts of the body. Many of the cancer cells that break off from the original tumor die without causing any problems. But some settle in a new area. There, they grow and form new tumors. When cancer spreads, we say that it metastasizes. If there’s only a single tumor, it’s called a metastasis or a metastatic tumor. When there are 2 or more metastatic tumors, it’s called metastases.
Sometimes metastatic tumors are found on tests done when the primary cancer is first diagnosed. In other cases, the metastasis is found first, causing the doctor to look for the place that the cancer started. Different cancers tend to spread to different sites, but some of the most common sites of metastasis are the bones, liver, brain, and lungs.

A bone metastasis is an area of bone that contains cancer that spread there from somewhere else. Cancer can spread to any bone in the body, but metastases are most often found in bones near the center of the body. The spine is the most common site. Other common sites are the hip bone (pelvis), upper leg bone (femur), upper arm bone (humerus), ribs, and the skull. Once cancer has spread to the bones or to other parts of the body it’s rarely able to be cured. Still, it often can be treated to shrink, stop, or slow its growth. Even if a cure is no longer possible, treating the cancer may be able to help you live longer and feel better.
Cancer cells can affect the bones by interfering with osteoblasts and osteoclasts:
· Often, the cancer cells make substances that turn on the osteoclasts. This leads to bone being broken down without new bone being made. This weakens the bones. The holes that develop when parts of bones dissolve are called osteolytic (OS-tee-oh-litik) or lytic (LIT-ik) lesions. Lytic lesions are so weak that they can cause the bone to easily break.
· Sometimes, the cancer cells release substances that turn on the osteoblasts. This leads to new bone being made without breaking down the old bone broken down first. This makes areas of the bones harder, a condition called sclerosis. The areas of bone where this occurs are called osteoblastic or blastic lesions. Although these blastic areas are harder, the structure of the bone is not normal and these areas actually break more easily than normal bone.

Bone metastasis can cause other problems as well:
· When cancer spreads to the bones of the spine, it can press on the spinal cord. This can cause nerve damage that may even lead to paralysis if not treated.

· As cancer cells damage the bones, calcium from the bones is released into the blood. This can lead to problems caused by high blood calcium levels (hypercalcemia [HIper- kal-SEE-me-uh]).

 BONE METASTASES MECHANISM


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