Glossary
MULTIPLE MYELOMA
Multiple myeloma is a form of cancer that affects plasma cells, a fundamental component of the immune system. Plasma cells are the result of the maturation of B lymphocytes; together with T lymphocytes (T-cells), these represent the two main cell types involved in the immune response. Plasma cells can mainly be found in the bone marrow and their role is to produce and release antibodies to fight infections. However, their growth occasionally proceeds in an uncontrolled manner, giving rise to a tumor. Myeloma cells produce large quantities of a protein known as monoclonal component (M Component), a particular type of antibody. The abnormal growth of plasma cells gives rise to problems to other blood cells (white blood cells, red blood cells and platelets) weakening the immune system, leading to anemia or defects in coagulation. Furthermore, myeloma cells produce a substance that stimulates osteoclasts, which are responsible for the destruction of the bone tissue; consequently, myeloma patients are often subject to bone fractures.
Types of Multiple Myeloma
Myeloma is an alteration of the plasma cells, but can occur in different forms.
• Multiple myeloma: the most frequent. Tumor plasma cells are mainly located in the bone marrow and produce a monoclonal antibody that can be identified in large quantities within the serum of the patient.
• Light Chain myeloma: plasma cells only produce parts of immunoglobulins known as light chains.
• Non-secretory myeloma: plasma cells do not produce immunoglobulins, but are present in excessively large numbers.
• Solitary plasmacytoma: the tumor occurs in a single location, within a bone or at extra-medullary level.
• Plasma cell Leukemia: plasma cells are present in large numbers also in the blood.
• Indolent myeloma: the disease is asymptomatic and there are no lesions to bones or other organs.
Evolution
Following the diagnosis, it is vital to define the stage of myeloma, according to which indications are also obtained regarding the prognosis of the disease. The Durie-Salmon system is the traditional method to assign a stage to myeloma. It identifies three stages taking into account four factors: amount of immunoglobulins in the blood or urine, the amount of calcium in the blood, the amount of hemoglobin in the blood and severity of bone damage (assessed by means of X-ray). However, the accuracy of this system is decreasing, as new diagnostic techniques are being introduced. The International System of staging of multiple myeloma is another staging system that has recently been introduced to define the three stages of myeloma. This system is mainly based on the levels of serum albumin and beta-2-microglobulin as well as on the renal function, on platelet count and age of the patient. In some cases, the tumor recurs after treatment: this is known as recurring myeloma, which may arise again in the bones or elsewhere in the body. Lastly, indolent myeloma is a tumor that displays neither active nor rapid growth, and thus causes no damage to bones or other organs. Because of the characteristics of this disease, patients with indolent myeloma generally do not undergo treatment, but are rather kept under careful observation
Diagnosis
Early diagnosis of multiple myeloma is difficult, since patients do not usually have any symptoms until more advanced stages. Similarly, they may have general symptoms, which could be caused by other diseases. Blood and urine tests provide a preliminary indication of the presence of a tumor of plasma cells. By means of electrophoresis on serum and urine proteins, high levels of immunoglobulins indicate the presence of the disease.
In addition to these techniques, analysis on other serum parameters may help to define the presence of myeloma, albeit not essential for the diagnosis. Specifically, hemoglobin and platelets levels are low in the presence of the disease, and at advanced stages of the tumor. The same is true for serum albumin levels. Also high levels of beta-2 microglobulin and calcium in the serum indicate the advanced stage of a myeloma. Bone marrow biopsy is a fundamental tool for the diagnosis of myeloma, which involves extracting and analyzing a fragment of bone and bone marrow. The bone marrow is aspirated with the use of a syringe (bone marrow aspirate) and analyzed for the presence of any cancer cells. Other techniques, including medical imaging techniques such as X-rays, CT, MRI and PET, are also used in order to complete and optimize the diagnosis of myeloma.
See also:
• Glossary