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Abstract
Microtype BCR/ABL rearrangement is extremely rare and has been known to be associated with neutrophilic chronic myeloid leukemia (N-CML). However, there is more to be understood regarding this phenotype. We report a case of atypical CML that exhibited micro BCR/ABL rearrangement with predominant thrombocytosis. Our patient showed thrombocytosis (1,464×109/L) and megakaryocytosis in the peripheral blood and bone marrow. However, neither leukocytosis nor neutrophilia was observed (white blood cells (WBC), 5.02×109/L neutrophils, 45%). Bone marrow aspirate revealed increased cellularity: 12% basophils, 6% eosinophils, and 9% blasts. The 46,XX,t(9;22)(q34;q11.2),i(17q) chromosome complement was observed in 4 of 20 metaphase cells, and standard BCR/ABL fusion signals were observed in 10% of interphase cells on fluorescence in situ-hybridization (FISH) analysis. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to acquire the BCR/ABL fusion transcript, the identity of which was confirmed via sequence analysis. Hematologic remission was achieved 2 months after imatinib therapy initiation, and molecular remission was achieved 2 months after hematologic remission. The patient is currently undergoing regular follow-up visits and is in good health. However, further long-term follow up is warranted. The incorporation of imatinib into therapeutic strategies may be further established through the study of more cases of micro BCR/ABL.
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 | Fig. 1Bone marrow aspiration smear (A, wright stain, ×1,000) and bone marrow biopsy (B, H&E stain, ×200). (A) The bone marrow aspirate shows increased blasts (9%), basophils (12%), and eosinophils (6%). (B) Biopsy shows increased cellularity and proliferation of hypolobulated megakaryocytes. |
 | Fig. 2FISH analysis of BCR/ABL fusion. The interphase cell have one separate green (BCR), one separate red (ABL) and two fusion signals consistent with the presence of a BCR/ABL fusion. |
 | Fig. 3RT-PCR for the BCR/ABL gene. Lane 1, micro BCR/ABL rearrangement cells of the patient; Lane 2, negative control; Lane 3, positive control with major BCR/ABL rearrangement; M, size marker. |
 | Fig. 4Sequence analysis. The vertical arrow marks the junction between BCR exon 19 and ABL exon 2. |
Table 1.
Clinical and hematologic chracteristics of the 21 cases with e19a2 junction transcripts reported in the literature
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