Morphologic and cytogenetic study. (A) Peripheral blood smear and (B) bone marrow aspirates show myeloblasts, immature monocyte precursors, and abnormal eosinophils. The eosinophil count is markedly increased (53.4%), and some eosinophils have basophilic granules (Wright Giemsa stain ×1,000). (C) Blasts are positive for myeloperoxidase (MPO). (D) The marrow monocytic component is stained by α-naphthyl-butyrate esterase. (E) The karyotype reveals 46,XX,inv (16)(p13.1q22)[20] (GTL banding, ×1,000). (F) FISH using a LSI CBFB Dual Color Break Apart Rearrangement Probe reveals separate red (5' CBFB gene) and green (3' CBFB gene) signals, resulting in distinct hybridization signals on the arm of the inverted chromosome 16, and these signals were expressed in more than 89% of the cells. The normal CBFB allele is seen as one fused red-green (yellow) signal.

K-ras mutation by pyrosequencing. Pyrogram shows the mutation and mutated clones. The X axis means the base and the Y axis represents the intensity of fluorescent signal. Shaded regions represent K-ras codons 12 and 13. (A) Arrow shows the analytic results of substitutions in the second base of K-ras codon 12. The mutation GGT (Gly) to GAT (Asp) in codon 12 was detected by pyrosequencing. (B) After induction of chemotherapy, the K-ras mutation disappeared.