A case of a mantle cell lymphoma with abundant and irregular cytoplasm: When you go with the flow

We would like to report the case of a 77-year-old man presented with general health deterioration for 1 month, including a 4 kg weight loss and important night sweats. Clinical examination revealed cervical and bilateral axillary lymphadenopathies as well as a palpable spleen extending 11 cm below the left costal margin. Biological investigations showed microcytic anemia (hemoglobin 98 g/L), hyperleukocytosis (white blood cell count 19 × 109/L) without thrombocytopenia. Biochemical assessments of iron status revealed low serum iron at 2.5 μmol/L and ferritin at 63 ng/mL. Lactate dehydrogenase (LDH) was slightly elevated at 268 IU/L (N < 250 IU/L) and β-2 microglobulin was also increased at 5.8 mg/L. An inflammatory syndrome was noted with elevated α-2 microglobulin at 9.2 mg/L (N < 8.5 mg/L) and CRP at 54.9 mg/L. Gamma globulin levels were within normal range (9 g/L), with no monoclonal spike. Other laboratory parameters were within normal limits. Peripheral blood smear examination revealed numerous medium-sized lymphocytes with regular nuclei, mature and nucleolated chromatin and relatively abundant cytoplasm showing irregularities (Figure 1). Flow cytometry analysis showed a monotypic mature B-cell lymphoproliferation expressing lambda light chain. The immunophenotype of this population was CD5+, CD10−, CD23−, CD20+, FMC7+, CD200−, CD180low, and CD43− (Figure 2). The Moreau score was 1. Flow cytometry was performed using our B-lymphoma panel, which does not include CD11c. Cytological data in association with immunophenotyping (CD10−, CD43−, and CD180low) suggested a leukemic phase of an indolent B-cell lymphoma, most likely marginal zone lymphoma (Chiriac et al., 2025). Even though CD5 positivity combined with CD200 negativity is more suggestive of mantle cell lymphoma. the study of cyclin D1 and SOX11 expression was not performed. Cytogenetic analysis revealed a complex karyotype. with loss of chromosome Y and chromosome 5, and a t(11;14)(q13;q32) translocation in 7 of the 15 metaphases analyzed. Fluorescence in situ hybridization (FISH) confirmed the presence of an IGH::CCND1 rearrangement in 8 of 10 nuclei evaluated. These findings established the final diagnosis of leukemic phase mantle cell lymphoma (MCL). It should be noted that 3 of the 15 mitoses analyzed by FISH showed 3 copies of the MYC locus (8q24) without rearrangement. The discrepancy between the low proportion of cells harboring the t(11;14) translocation, even though most lymphocytes were monotypic, together with the presence of additional subclonal abnormalities detected by FISH, suggests clonal heterogeneity. Regarding serum immunoglobulin, MCL frequently presents a normal level of gamma globulin or only mildly decreased, and hypogammaglobulinemia is considered uncommon. Unlike other B-cell lymphomas, the tumor cells in MCL do not show differentiation into plasma cells (Jain & Wang, 2019). MCL is also known for its cytological heterogeneity across individuals. Nonetheless, these pathological lymphoid cells are commonly large, with irregular nuclei and minimal cytoplasm. In this case, the presence of moderately abundant cytoplasm and cytoplasmic irregularities is atypical for MCL, underlining the morphological variability of this entity. The authors would like to thank all the technical staff who carried out the analyses and contributed to this study. The authors declare no conflicts of interest. No ethical approval was necessary for this case. There is no patient-identifiable data included in this case report. There is no data available for this study.