Figure 1: Bone marrow morphology and karyotype analysis: A) Bone marrow smear stained with Wright-Giemsa, showing that this was a rare case of APL with hypogranular variant morphology (M3v). Promyelocytes appeared in the bone marrow aspiration prior to treatment (promyelocytes 91.5%). The cell body was of different size, containing much cytoplasm and few A particles (also known as azurophilic granules). The nuclear distortion was obvious and typically of butterfly or dumbbell shape. B) Complete remission was achieved post-treatment (promyelocytes 1%). C) Karyotype analysis revealed 44,XY, t(15;17)(q22;q21),-1,-8 [1]/ 46,XY, t(15;17) (q22;q21) [6] /46,XY [3]. The clone with the translocation t(15;17)(q22;q21) as the main abnormality was the stem line. One additional abnormal subclone was identified, with loss of a single chromosome on chromosomes 1 and 8 respectively.