High‐grade B‐cell lymphoma developed during the treatment of chronic myeloid leukemia with bosutinib

Tyrosine kinase inhibitor (TKI) can help to increase the survival time in chronic myeloid leukemia (CML) patients; however, the risk of secondary malignancies due to TKIs is a growing concern. Only few reports showed clinical course of patients who developed lymphoma during TKI therapies. Herein, we report a case of high‐grade B‐cell lymphoma diagnosed in the course of CML treatment with bosutinib. The 75‐year‐old male patient had been diagnosed with CML 25 years ago. After receiving TKIs (imatinib, nilotinib, and bosutinib), he achieved a major molecular response. Over 3 years after starting bosutinib, he was diagnosed with a high‐grade B‐cell lymphoma. A total of six courses of DA‐EPOCH‐R therapy brought complete remission of the lymphoma. Moreover, BCR‐ABL1 transcript copies remained undetectable by RT‐PCR, 8 months after stopping bosutinib. The risk of secondary malignancy due to TKI has been controversial. It is reported that TKI induces irreversible chromosomal abnormalities or chromosome aberrations and inhibits the proliferation or function of T cells, B cells, and NK cells. These mechanisms of TKI may contribute to the development of secondary malignancy. There remains no consensus on the management of secondary lymphoma during TKI therapies. At present, the only alternative is to observe patients receiving TKI treatment cautiously and to treat secondary lymphoma in the same manner as de novo lymphoma.