Lymphoid disorders other than common acute lymphoblastic leukemia: background.

The cytogenetic abnormalities that are found in chronic lymphoid malignancies (and in acute leukemias deriving from relatively mature cells) fall mainly into two groups according to whether the malignant cells are of B-lineage or T-lineage. In most of the B-lineage cases. there is some abnormality of the IgH gene which is located at 14q32 or, less frequently, the other immunoglobulin genes located at 2p12 and 22q11. In the T-lineage cases, there is often some abnormality involving the T-cell receptor loci, most frequently those at 14q11. Other abnormalities occur, but few have a close association with a particular disease type, and so do not often contribute to determining a precise diagnosis. This lack of specificity is due partly to deficiencies in our understanding of the biological relationships between different lymphoid disorders, and also to the various classifications that have been used. As a consequence, there has to be some doubt about the diagnosis assigned to many of the cases in published cytogenetic studies. It is also difficult to combine data from series that have used different classification systems. The present unsatisfactory situation greatly limits the clinical usefulness of cytogenetic studies and there is a real need to unravel the complexities of this large family of malignancies.