DETECTION OF THE BCR-ABL GENE BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION AND FLUORESCENCE IN-SITU HYBRIDIZATION IN A PATIENT WITH PHILADELPHIA-CHROMOSOME NEGATIVE ACUTE LYMPHOBLASTIC-LEUKEMIA

The Philadelphia (Ph) chromosome is detected in leukaemia cells in approximately 20% of adults with acute leukaemia (ALL). When treated with chemotherapy therapy alone, Ph-positive ALL has a poor prognosis, and patients may benefit from bone marrow transplantation in first remission. Here we report a patient with chromosomally normal bone marrow, in all 60 cells analysed, who was found to have the p210-type BCR-ABL chimaeric transcript by RT/PCR. Fluorescence in situ hybridization was labelled cosmid probes for BCR and ABL showed the presence of BCR-ABL juxtaposition on a normal chromosome 22 in leukaemia cell metaphases. We conclude that molecular and cytogenetic methods should be used in conjunction to detect the BCR-ABL gene rearrangement in ALL.