Detection and diagnostic value of t(14;18) translocation in minimal residual disease of follicular lymphoma

The minimal residual disease is important in several malignant diseases, such as in hematopoietic malignancies (e.g. in follicular lymphoma) or in solid tumors, due to the presence of a tumor burden following a treatment of these diseases. In case of t(14;18) chromosome translocation, which characterizes most of the follicular lymphomas, the bcl-2 gene translocates to the joining region of the immunoglobulin heavy chain of chromosome 14. The expression of bcl-2 gene alters due to the translocation, and this change results in the inhibition of cellular apoptotic processes, and in turn these series of events may finally lead to the development of lymphoma. It is inevitable to learn the results of radio- and/or chemotherapy, i.e. whether the translocation-bearing cells disappeared from the lymphocytes of peripheral blood as well as from that of bone marrow, or we have to take into account the minimal residual disease. Using nested-PCR one can detect the translocation in 1 out of 10(5) cells, this way the results of the treatments can be controlled: one can establish the emergence of remissions; and the relapses could also be detected earlier than by using conventional diagnostic methods. Our experience, yielded by the follow up studies of follicular lymphoma patients, shows that the results of PCR detection correlate excellently with the conclusions of other diagnostic techniques. Nevertheless, the t(14;18) translocation-bearing cells can also be detected in peripheral lymphocytes of healthy donors as well as in that of different diseases of other types than lymphoma, but not in bone marrow. Therefore we emphasize the importance of the translocation-detection in the bone marrow of the patients of follicular lymphoma. More and more advanced techniques have made it possible to detect the minimal residual disease, this way it will be easier to diagnose and to predict the outcome of different malignant diseases.