 Because acute promyelocytic leukemia ( APL ) has the highest curability and requires 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 identifies the chromosomal translocation [ t ( 15 ; 17 ) ( q22 ; q12 ) ; ] that characterizes APL . There is also a need to molecularly detect the presence of PML / RARA fusion protein , which is an oncogenic product of that translocation . 
