HHV8-negative primary effusion-based large B-cell lymphoma in a patient with chronic myeloid leukemia, BCR::ABL1-positive under dasatinib treatment: Report of a new case and literature review.

Dasatinib, a second-generation tyrosine kinase inhibitor (TKI), used as treatment for chronic myeloid leukemia, BCR::ABL1-positive (CML), is complicated by pleural or pericardial effusions in about one-third of patients. Besides, in exceptional instances, effusion-based neoplastic B-cell lymphoproliferations have been described. Here, we report an HHV8-negative, EBV-positive large B-cell lymphoma presenting as a pericardial effusion in a patient with CML treated with dasatinib for 23 months, without associated tumor mass or lymphadenopathies. Large tumor cells showed a B-cell phenotype (CD20+, CD79+), with evidence of EBV infection (EBER-ISH+), but HHV8 (LANA-1) negative. Monoclonal IG gene rearrangements were identified. BCL2, BCL6, and MYC genes were not rearranged. Despite the aggressive cytomorphology the patient was in complete remission after 4 cycles of R-CHOP after 8 months follow-up. Four other cases of large B-cell effusion-based lymphomas developed in the setting of dasatinib therapy for CML have been reported in the literature. The four cases were HHV8-negative and one case was EBV-positive. Three of the four patients experienced a benign clinical course, which is in contrast to HHV8-positive primary effusion lymphoma (PEL). The mechanisms of development of these effusion-based B-cell lymphoproliferations in patients receiving TKI are not completely elucidated. Acute or relapsing effusions during TKI treatment in the setting of CML should be cytologically examined to exclude clonal B-cell lymphoproliferations.