BCL2-Rearrangment-Negative CD23+ Follicle Center Lymphoma and Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma: A Rare Case of Biclonal Composite Lymphoma.

Composite lymphomas are rare and diagnostically complex, comprising two or more distinct lymphoma subtypes within the same anatomical site and often requiring a comprehensive diagnostic approach. Due to their rarity and varied presentations, further research is needed to better understand their pathogenesis, clonal relationships, and optimal management strategies. This case report highlights an unusual presentation of composite lymphoma involving the coexistence of BCL2-R-negative, CD23-positive follicle center lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).