Concurrent Presentation of Hairy Cell Leukemia and Mantle Cell Lymphoma (Leukemic Non-Nodal Variant): An Extremely Rare Composite Lymphoma

Abstract

Herein, we describe the clinicopathologic and genetic characteristics of the first report of simultaneous bone marrow involvement by classical hairy cell leukemia (HCL) and leukemic non-nodal variant of mantle cell lymphoma (L-NN-MCL) with t(11;14)(q13;q32) with BRAF mutation and deletion of TP53. A 40-year-old asymptomatic man was investigated for incidental neutropenia and thrombocytopenia. Flow cytometry showed two distinct monotypic B-cell populations: one expressed CD19 (bright), CD20 (bright), FMC7, CD103, CD25, CD11c, CD123, and IgD (bright) and showed kappa light chain restriction (bright), consistent with HCL and the other kappa-restricted CD5/CD10-negative B-cell population with distinctive immunophenotypic features. The bone marrow biopsy is infiltrated by an abnormal B-lymphoid infiltrate with different patterns of infiltration in different marrow areas. Fluorescence in situ hybridization (FISH) analysis revealed a CCND1/IGH rearrangement, t(11;14)(q13;q32), and deletion of TP53. The BRAF V600E missense mutation was detected by quantitative real-time polymerase chain reaction (PCR). The diagnosis of a composite B-cell neoplasm was composed of HCL together with a second CD5/CD10-negative monotypic B-cell population, with CCND1/IGH fusion, favoring the 2016 WHO new category of L-NN-MCL (CD5/SOX11-negative). Treatment with cladribine and rituximab normalized the blood counts within 6 weeks without significant side effects. L-NN-MCL is one of the smoldering MCL subtypes, recently listed in WHO 2016 as a separate variant, with a particular set of unique features and a less aggressive clinical course compared to classical MCL. To date, the clinicopathological features (including the bone marrow findings) of L-NN-MCL have not been sufficiently characterized in the literature. We describe the first report of synchronous presentation of HCL and L-NN-MCL. This case represents a real challenge from the biologic, diagnostic and therapeutic point of views, due to extremely rare combination of two distinct uncommon B-cell neoplasms. The study of composite lymphomas offers the opportunity to evaluate the etiology and the clonal interrelationship involved in the pathogenesis/evolution of lymphomas.

J Hematol. 2022;11(1):21-28
doi: https://doi.org/10.14740/jh942