A chronic myeloid leukemia case with a variant translocation t(11;22) (q23;q11.2): masked Philadelphia or simple variant translocation?

Chronic myeloid leukemia (CML) is characterized by the presence of the Philadelphia chromosome (Ph), usually due to a reciprocal translocation, t(9;22)(q34;q11.2). The remaining cases (2-10%) have variant translocation, and more rarely (~1%) a cryptic rearrangement is present which can be detected by fluorescence in situ hybridization analysis in a CML patient with a Ph-negative karyotype (Masked Ph). We present a masked/variant BCL-ABL-positive CML patient showing a t(11;22)(q23;q11.2) which was detected using a combined approach of conventional cytogenetics and reverse transcription polymerase chain reaction. In February 2013, the patient was diagnosed as having CML. Imatinib mesylate (400 mg/day), was then started. Under imatinib therapy a complete hematologic and cytogenetic response was attained. In December 2013, an increment in BCR-ABL/ABL transcript levels according to the International Scale (from 0.0471% to 1.4034%), indicating imatinib failure, was documented. Administration of nilotinib (400 mg twice daily) resulted in durable molecular response after 3 months. The patient is still on nilotinib treatment throughout the observation period with no sign of recurrence and adverse events.