[The appearance of t(9;22)(q34;q11.2) in BJP-λ type multiple myeloma during maintenance therapy including lenalidomide].

A 61-year-old man, who was diagnosed with Bence-Jones protein (BJP)-λ type multiple myeloma, was treated with bortezomib. Although maintenance therapy including lenalidomide was continued, t(9;22)(q34;q11.2) was detected in the marrow cells by a cytogenetic study. The increased incidence of a secondary malignancy after treatment with lenalidomide for multiple myeloma has been highlighted in previous clinical trials; however, reports on the presence of t(9;22)(q34;q11.2) or the onset of chronic myelogenous leukemia have yet to be found. Although the cause of chronic myelogenous leukemia with the lenalidomide treatment is not yet clear, it is an interesting case.