what is myeloma

You have probably heard the terms “multiple myeloma” and “myeloma”. These terms refer to the same thing: a cancer of the plasma cells. Plasma cells are found in the bone marrow, the hollow area within the bones. Because plasma cells are found in the blood, myeloma is referred to as a hematologic or blood cancer. It may also be referred to as plasma cell myeloma. The word “multiple” is often used because the malignant cells usually affect multiple areas of the bone marrow.

Your bone marrow is a sort of “blood factory” where three kinds of blood cells are made:

1. Red blood cells that carry oxygen
2. Cells called platelets (or thrombocytes) that help the blood to clot whenever you cut yourself
3. A variety of white blood cells including lymphocytes that plays important roles in the functioning of your immune system.

There are two types of lymphocytes: T cells and B cells. Another variety of white blood cell you may hear of is the neutrophil. This plays an important role in protection from infection. If you are receiving chemotherapy and have a low neutrophil level you are more susceptible to infection. With regard to lymphocytes:

• The abbreviation "T", in T cell (or T lymphocyte), stands for thymus since it is the principal organ for their development.
• B cells (or B lymphocytes) are found in the bone marrow. As they mature, B cells turn into plasma cells.

When plasma cells are exposed to antigens or foreign substances, they produce different antibodies. These antibodies are called immunoglobulins (the short form is Ig). Immunoglobulins are proteins made up of two types of chains:

• heavy chains (G, A, M, D or E type) 
• light chains (kappa, k, or lambda, l)

Normally, the most common immunoglobulin in the blood is IgG, followed by IgA and IgM. IgD and IgE are usually present in the blood in only very small amounts.

what happens when you have myeloma

In myeloma, the B lymphocyte (the cell that matures into a plasma cell) is damaged. It begins to reproduce plasma cells uncontrollably. We commonly refer to this “good cell gone bad” as being malignant.

When plasma cells reproduce uncontrollably, two things happen.

1. Too many plasma cells are produced. In healthy people, plasma cells make up two to three percent of the cells in the bone marrow. In someone who has myeloma, plasma cells make up at least ten percent of the cells – or even more. The abnormally high number of plasma cells can “crowd” out other types of cells you need to be healthy, such as red blood cells or platelets.
2. Too much of the same immunoglobulin is produced, such as too much IgG or IgA. This is referred to as the monoclonal protein (M-protein), monoclonal spike (M-spike), monoclonal peak (M-peak), or paraprotein.

When myeloma cells enter the bone marrow, they attach to other, structural cells of the bone marrow known as stromal cells. Once attached to stromal cells, interactions occur that stimulate the myeloma cells to continue reproducing.

• Chemical messengers called cytokines are produced that stimulate the growth of myeloma cells and prevent the cells from dying naturally. Interleukin 6 (IL-6) is one of these chemical messengers.
• The myeloma cells secrete chemicals called growth factors that promote the creation of new blood vessels (a process called angiogenesis). One of the most important of these growth factors is vascular endothelial growth factor (VEGF).
• The immune system begins to fail. Ordinarily your immune system would try to clear out or stop the growth of abnormal cells. But as the immune system weakens, it is unable to battle the abnormal cells.

As the myeloma cells invade the bone, they cause multiple areas of damage that weaken the bone. These areas are known as osteolytic lesions, or lytic lesions for short.

Sometimes, the myeloma cells collect in a single bone and form a tumour called a plasmacytoma. Occasionally, plasmacytoma can even affect areas of soft tissue outside of bone. 

 

Note that the following terms can be used interchangeably:

• multiple myeloma = myeloma

• M-spike = M-protein = myeloma protein = paraprotein