[Chronic-phase chronic myeloid leukemia complicated by dasatinib-associated lymphadenopathy].

A 55-year-old man was diagnosed with chronic myeloid leukemia (CML) in the chronic phase and achieved a major molecular response (MMR) 3 months after dasatinib induction. Seven months later, he noticed left cervical lymphadenopathy, and 18-fluorodeoxyglucose positron emission tomography (FDG-PET) showed marked 18F-FDG uptake at the left cervical and supraclavicular lymph nodes. Left cervical lymph node biopsy showed reactive follicular hyperplasia and increased numbers of large B-cells between the follicles. Based on the clinical course, dasatinib-associated lymphadenopathy (DAL) was diagnosed. The treatment was switched to bosutinib, and lymph node enlargement resolved after 4 weeks. Lymphoproliferative disorder during CML treatment is a rare adverse event of dasatinib and is classified in the category of immune deficiency and dysregulation-associated LPDs (IDD-LPDs) in the WHO Classification of Tumours, 5th Edition. As more new drugs associated with IDD-LPDs are used across various indications, the scope of iatrogenic immune deficiency-related LPDs continues to broaden. Although the pathogenesis of DAL remains unclear, the immune dysregulation mechanisms of dasatinib may contribute. Since spontaneous remission can be expected with dasatinib discontinuation, observation should be considered even when differentiation from de novo lymphoma is difficult, and the decision to initiate chemotherapy should be made carefully.