A20 (TNFAIP3) Alterations in Primary Intestinal Diffuse Large B-cell Lymphoma

The gastrointestinal (GI) tract is the most frequently involved site of extranodal non-Hodgkin lymphomas, and diffuse large B-cell lymphoma (DLBCL) is the most common subtype occurring in the GI tract. TNFAIP3 (A20) genetic alterations were reported to be involved in DLBCL’s pathogenesis and a portion of GI-DLBCL cases harbor this alteration. However, the frequency and clinicopathological relations focusing on small and large intestinal DLBCL are unclear. Here, we examined A20 deletion and protein expression and analyzed the clinicopathological features of 52 cases of primary intestinal DLBCL. The most frequently involved site was the ileocecal region (75%), followed by small bowel (13.5%) and large intestine. Immunohistochemically, the ileocecal cases expressed BCL6 (p=0.027) and MUM1 (p=0.0001) significantly more frequently than the small intestinal cases. Six of 47 cases (13%) had A20 heterozygous deletion, whereas all 6 heterozygously deleted cases had detectable A20 protein expression. In summary, A20 abnormality was less prevalent among intestinal DLBCLs with some discordancy between gene deletion and protein expression. Although the A20 alteration status did not affect any clinicopathological characteristics in this series, further studies exploring alterations of A20 and other NF-κB components in primary intestinal DLBCL are needed

Low-grade B-cell lymphoma presenting primarily in the bone marrow

Cases of low-grade B-cell lymphoma presenting primarily in the bone marrow are rare, and its clinicopathology remains unclear. We retrospectively examined patients with low-grade B-cell lymphoma presenting primarily in the bone marrow. Fourteen patients met the inclusion criteria, including 5 with lymphoplasmacytic lymphoma (LPL), 3 with chronic lymphocytic leukemia/small lymphocytic lymphoma, 2 with follicular lymphoma (FL), and 4 with low-grade B-cell lymphoma not otherwise specified (LGBCL-NOS). The median age was 69.5 years (range, 42-89 years), and a slight male predominance was noted (9 men and 5 women, 1.8: 1). Immunohistochemically, all cases were positive for CD20. One case was positive for CD138. Both cases of FL were positive for CD10 and B-cell lymphoma 2 (BCL-2), and immunoglobulin heavy locus (IgH)/B-cell lymphoma 2 rearrangement was observed by fluorescence in situ hybridization. The myeloid differentiation primary response gene (88) leucine to proline mutation was observed in 3 of 5 LPL, 1 of 2 FL, and 2 of 4 LGBCL-NOS patients. Paraproteinemia was observed in 10 patients; IgM and IgG paraproteinemia were observed in 6 and 3 patients, respectively. In this patient series, 3 patients had died at a median follow-up of 36.5 months; the cause of death of 1 LPL patient was malignant lymphoma itself. Thus, low-grade B-cell lymphoma presenting primarily in the bone marrow has various subtypes, and approximately one-third of the patients had LGBCL-NOS. The immunophenotypic features and myeloid differentiation primary response gene (88) leucine to proline mutation data of LGBCL-NOS suggested that some cases present with characteristics similar to those of LPL or marginal zone lymphoma

Single cell transcriptome analysis reveals disease-defining T cell subsets in the tumor microenvironment of classic Hodgkin lymphoma

Hodgkin lymphoma is characterized by an extensively dominant tumor microenvironment (TME) composed of different types of noncancerous immune cells with rare malignant cells. Characterization of the cellular components and their spatial relationship is crucial to understanding cross-talk and therapeutic targeting in the TME. We performed single-cell RNA sequencing of more than 127,000 cells from 22 Hodgkin lymphoma tissue specimens and 5 reactive lymph nodes, profiling for the first time the phenotype of the Hodgkin lymphoma–specific immune microenvironment at single-cell resolution. Single-cell expression profiling identified a novel Hodgkin lymphoma–associated subset of T cells with prominent expression of the inhibitory receptor LAG3, and functional analyses established this LAG3+ T-cell population as a mediator of immunosuppression. Multiplexed spatial assessment of immune cells in the microenvironment also revealed increased LAG3+ T cells in the direct vicinity of MHC class II–deficient tumor cells. Our findings provide novel insights into TME biology and suggest new approaches to immune-checkpoint targeting in Hodgkin lymphoma. SIGNIFICANCE: We provide detailed functional and spatial characteristics of immune cells in classic Hodgkin lymphoma at single-cell resolution. Specifically, we identified a regulatory T-cell–like immunosuppressive subset of LAG3+ T cells contributing to the immune-escape phenotype. Our insights aid in the development of novel biomarkers and combination treatment strategies targeting immune checkpoints