[DNA diagnosis of human cancers: lymphoid malignancies and leukemia]

Usefulness of DNA analysis in diagnosis of hematopoietic malignancy was discussed. Examination on the presence of rearrangement in immunoglobulin (Ig) and T cell receptor (TCR) was the first DNA analysis used for clinical diagnosis of lymphoid malignancy to determine the cell-lineage and clonality of proliferating lymphoid cells. One point mutation in ras oncogene has also been used to detect residual leukemic cells as well as diagnosis of the early relapse of leukemia, although not all leukemic cells have this mutation. Presence of BCR-abl fused gene is a genetic marker for Ph1 chromosome. Analysis of BCR-abl gene has made it possible to diagnose the Ph1 ALL and masked Ph1 CML. Development of PCR technique markedly increased the possibility for the use of DNA analysis in clinical medicine. In addition to Ph1 chromosome, various chromosomal abnormalities resulted in a reciprocal translocation between Ig or TCR gene and other genes in various lymphoid malignancies, such as Burkitt lymphoma and follicular lymphoma. These translocations can be analyzed by Southern hybridization and used for clinical diagnosis.