Insertion of BCR in the ABL1 locus detected by FISH tests in a female patient with newly diagnosed CML

Conventional chromosome analysis of a bone marrow aspirate specimen from a female patient with newly diagnosed CML shows a normal female karyotype in all 20 metaphase cells; both pairs of chromosomes 9 and 22 appear normal (A). FISH analysis using a dual fusion probe set for BCR (22q11.2, labelled with green) and ABL1 (9q34.1, labelled with red) detects a BCR::ABL1 fusion on one of the normal looking chromosome 9 (arrow) in 99.7% of cells, indicative of an insertion of BCR to one ABL1 locus (B). Molecular testing revealed the BCR::ABL1 P210 transcript.