A translocation breakpoint at chromosome band 12q13 associated with B-cell chronic lymphocytic leukemia.

Low-grade B-cell lymphoproliferative disorders are frequently associated with an extra copy of chromosome 12. This well-documented acquired anomaly is one of the most specific numerical chromosome alterations to occur in human hematological malignancies. We have cytogenetically characterized bone marrow and peripheral blood cells from a patient with B-cell chronic lymphocytic leukemia (CLL) having a unique acquired translocation involving chromosomes 6 and 12, t(6;12) (p21.3;q13), which implicates band 12q13 as the site of the gene(s) important in this lymphoproliferative B-cell disorder. Aneuploidy, in the form of trisomy of chromosome 12, is not a requirement for neoplastic transformation in B-cell CLL, but gene rearrangement (present case) or nondisjunctional acquisition of additional copies of defective genes on chromosome 12 at band q13 may be involved in the genesis or progression of this disorder.