Because acute promyelocytic leukemia ( APL ) have the highest curability and require a unique form of treatment , it is important to quickly establish or exclude the diagnosis of this subtype of leukemia . Fluorescent in situ hybridization performed on blood or bone marrow is often used for this purpose , as it readily identify the chromosomal translocation [ t ( 15 ; 17 ) ( q22 ; q12 ) ; ] that characterize APL . There is also a need to molecularly detect the presence of PML / RARA fusion protein , which is an oncogenic product of that translocation .