Clinical and molecular characteristics of APL. The 3 features of APL are (A) a severe bleeding tendency due to fibrinogenopenia and disseminated intravascular coagulation, (B) accumulation of abnormal promyelocytes in bone marrow (top panel) and peripheral blood (bottom panel), and chromosomal translocation t(15;17)(q22;q21) (C) with the resultant fusion transcripts between PML and RARα (D). (C) t(15;17) detected by fluorescence in situ hybridization using PML-RARα dual-color, dual-fusion translocation probes (Vysis, Downers Grove, IL). (D) Schematics representing the formation of 15;17 reciprocal chromosomal translocations (top panel) and fusion transcripts (bottom panel). Stains were analyzed using an Olympus BX51 research microscope equipped with a 100×/1.30 numeric aperture (NA) oil objective (Olympus, Tokyo, Japan). Images were processed using Adobe Photoshop CS (Adobe Systems, San Jose, CA). Original magnification, ×1000.