Cancer is a disease in which cells grow in an abnormal way. They are supposed to divide in a controlled way to replace old or damaged cells. With multiple myeloma (MM), a certain type of blood cell grows and divides quickly, making more than are needed.

Cancer Cell Growth
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Normal Blood Cells and the Development of Multiple Myeloma

All blood cells start in the bone marrow as stem cells. Stem cells mature into many types of blood cells that have certain roles in the body. These are:

  • Red blood cells—Carry oxygen from the lungs to the organs and cells of the body.
  • Platelets—Fix broken blood vessels by making the blood clot to stop bleeding.
  • White blood cells—Helps the body fight infection and disease.
Bone Marrow Sites in Adults
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New, healthy cells are made in the bone marrow. This keeps the number of blood cells in a healthy range. With MM, too many plasma cells are made and they crowd out the bone marrow. Plasma cells are a type of white blood cell. This makes it hard for new, healthy cells to be made. The low numbers of healthy blood cells can cause problems with the immune system, interfere with the body getting enough oxygen, or cause problems with blood clotting.

The cancerous plasma cells leave the bone marrow and move around in the body in the lymph and blood streams. This keeps organs like the kidneys, heart, or bones from working as they should.

Grouping

MM is grouped by how fast it grows and what problem it is causing. It is possible for the cancer to be in one tumor in one place. It is grouped as:

  • Smoldering—Progresses slowly without symptoms.
  • Symptomatic—Bone, kidney, and blood cell problems are present and causing symptoms.

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