What is being tested?
This test detects characteristic changes (rearrangements) in specific genes in B-cells. This information can be helpful in diagnosing a B-cell lymphoma. For an explanation of gene rearrangement please see Common Questions - How common are B-cell gene rearrangements?
B-cells are a type of lymphocyte, a type of white blood cell (WBC) that produces antibodies in response to infections (viruses, bacteria or parasites) as well as other "foreign invaders" that the immune system wants to destroy. Like almost all cells in the human body, white blood cells contain DNA. They start out as stem cells and as they develop into mature cells they develop rearrangements in certain parts of their DNA called immunoglobulin genes. B-cell immunoglobulin genes rearrange themselves during the development of each cell so that each one can produce a unique immunoglobulin or antibody molecule. These rearrangements are normal. The antibodies produced by the B-cells collectively protect against many different kinds of infections. The final order in which the genes are rearranged is called a gene rearrangement profile. Within any normal population of B-cells, the cells and their gene rearrangement profiles are very diverse.
In a lymphoma, the B-cells in affected tissue (such as blood, bone marrow or lymph node) are identical and their gene rearrangement profiles are likewise identical. Lymphomas arise when an abnormal B-cell begins to produce numerous identical copies of itself (clones). The cloned cells grow and divide uncontrollably, crowding out normal cells.
A B-cell immunoglobulin gene rearrangement test evaluates the B-cells in a person's sample to determine whether the majority of B-cell rearrangement profiles are diverse or identical. This information, along with clinical signs and symptoms and results of other laboratory tests, can help clarify a person's diagnosis, or evaluate the persistence or recurrence of lymphoma.
According to the Australian Institute of Health and Welfare, about 5,700 new cases of non-Hodgkin lymphoma are diagnosed in Australia each year. The majority of non-Hodgkin lymphomas are B-cell lymphomas.
For additional details about B-cells and this testing, read more.
How is it used?
B-cell immunoglobulin gene rearrangement tests are used to help diagnose non-Hodgkin B-cell lymphomas and check for residual or recurrent disease after treatment.
Lymphomas arise when an abnormal B-cell begins to produce numerous identical copies of itself (clones). The cloned cells grow and divide uncontrollably, crowding out normal cells. There are many different types of B-cell lymphoma and each has different characteristics, prognosis, and therapy. Several classification systems have been used to describe them. The most recent is from the World Health Organization (for more on this, see the Lymphoma article).
Testing for B-cell lymphomas involves several types of tests:
A proliferation of B-cells can be benign or malignant. If, at this point, there is still no conclusion whether a person has a benign or malignant lymphocyte population, B-cell immunoglobulin gene rearrangement testing can be performed.
Testing may sometimes be performed to evaluate the effectiveness of lymphoma treatment, that is, to detect residual or recurrent disease, the continued presence of abnormal monoclonal B-cells.
When is it requested?
Testing is performed when a person has signs and symptoms that suggest a lymphoma, such as:
Findings from a FBC and differential may be the first indication that a person might have a blood cell cancer as symptoms of early lymphoma may be absent, mild, or nonspecific.
Testing may be done when other laboratory tests indicate that a lymphoma may be present and/or when other tests are inconclusive. Some examples include:
Testing may also be ordered when a person has been treated for a lymphoma to evaluate the effectiveness of treatment, that is, to detect residual or recurrent disease.
What does the result mean?
Results of testing are typically interpreted by a pathologist and/or clinician who specialises in dealing with blood, blood cells, and bone marrow cells (haematologist). Results must be interpreted in conjunction with clinical findings, other test results including immunophenotyping information, an understanding of the strengths and limitations of different testing methods, and with an understanding of the range of findings in a "normal" lymphocyte cell population.
In general, if a significant clonal B-cell population is detected and other associated tests are in agreement, then it is likely that the individual tested has a B-cell lymphoma.
Examples of lymphomas that may be detected by gene rearrangement testing include:
Is there anything else I should know?
Each year in Australia, about 3,500 people are diagnosed with a type of B-cell or T-cell lymphoma making them the most common type of blood cancer diagnosed. Overall, they represent the sixth most common type of cancer in men, and the fifth most common type of cancer in women.
Sample collection and testing may need to be repeated when the initial sample does not contain enough DNA to test.
The detection of a clonal immunoglobulin gene rearrangement does not always indicate the presence of B-cell lymphoma. Someone may have a clonal B-cell population and not have cancer. Conditions such as autoimmune disorders, immune suppression, and immune deficiencies are sometimes associated with small clonal B-cell populations. This means that one or more groups of cloned B-cells may be present in a person's lymphocyte population without it being considered a lymphoma.
If someone is negative for a clonal B-cell immunoglobulin gene rearrangement, they may still have lymphoma. A test may also be negative if the test method is not sensitive enough to detect the rearrangement, or if the clonal lymphocytes have mutations that are not detected by the test.
Since false positive and false negative results can be associated with this testing, the results must be interpreted in the context of other clinical and pathologic findings.
Since plasma cells are terminally differentiated B-cells, immunoglobulin gene rearrangement testing can also be seen in plasma cell neoplasms, such as multiple myeloma and plasmacytoma.
No. This testing is only required if routine diagnostic procedures are not sufficient to make an accurate diagnosis.
No. A positive test result only helps to confirm a diagnosis of B-cell lymphoma and does not point to a specific subtype of B-cell lymphoma. The clinical course and response to treatment are generally determined by the subtype of a person's lymphoma, along with certain genetic abnormalities.
B-cell immunoglobulin genes are rearranged in each B-cell to produce unique immunoglobulins. These rearrangements are normal. The immunoglobulin genes consist of numerous, discontinuous coding segments. As B-cells develop and mature, a portion of DNA that contains one full DNA sequence of one of the genes breaks into pieces. After rearrangement, only some of the pieces are kept, which are joined back together in a specific set of steps. To visualise this, imagine that you have a piece of paper with a set of instructions on it, several paragraphs long and containing hundreds of words. Now imagine that you pick and choose words from multiple locations on the page – a sufficient number to form a sentence. Then you get rid of the rest of the words and put together your sentence. You started with a page and ended up with a sentence, but both make sense as you read them and, in this case, both represent "functional genes." It is not hard to see that many different sentences could have been constructed from the same set of instructions. In a similar fashion, the B-cell customisation process can be used to produce a large number of unique B-cell gene arrangements.
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