| Abstract: | In recent years, a subgroup of B‐cell precursor acute lymphoblastic leukemia (BCP ALL) without an established abnormality (“B‐other”) has been shown to be characterized by rearrangements of ABL1, ABL2, CSF1R, or PDGFRB (a.k.a. ABL‐class genes). Using FISH with probes for these genes, we screened 55 pediatric and 50 adult B‐other cases. Three (6%) of the adult but none of the childhood B‐other cases were positive for ABL‐class aberrations. RT‐PCR and sequencing confirmed a rare SFPQ‐ABL1 fusion in one adult B‐other case with t(1;9)(p34;q34). Only six SFPQ‐ABL1‐positive BCP ALLs have been reported, present case included. A review of these shows that all harbored fusions between exon 9 of SFPQ and exon 4 of ABL1, that the fusion is typically found in adolescents/younger adults without hyperleukocytosis, and that IKZF1 deletions are recurrent. The few patients not treated with tyrosine kinase inhibitors (TKIs) and/or allogeneic stem cell transplantation relapsed, strengthening the notion that TKI should be added to the therapy of SFPQ‐ABL1‐positive BCP ALL. |
