Atypical BCR-ABL mRNA transcripts in adult acute lymphoblastic leukemia.

RT-PCR detects chimeric BCR-ABL mRNA in approximately 25% of adult acute lymphoblastic leukemia (ALL) cases. Minor breakpoint transcripts (e1a2) are found in about 70% of positive cases and major breakpoint transcripts (e13a2, e14a2) in about 30% of cases. However, other atypical transcripts are sometimes observed. We report experience gained in the GMALL Study Group and identified 8 BCR-ABL-positive adult ALL cases with such atypical transcripts: 5 with e1a3, 2 with e13a3 (b2a3), and 1 with e6a2. This corresponds to a prevalence of 1-2% of all BCR-ABL-positive cases. The clinical courses are reported and diagnostic proposals are made.