Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive non-Hodgkin lymphoma (NHL) worldwide. Currently, approximately sixty percent of patients are cured with R-CHOP as frontline treatment, while the remaining patients experience primary refractory or relapsed (R/R) disease. Recently, the introduction of Pola-R-CHP as front-line therapy has represented a major advance in the management of DLBCL, resulting in improved outcomes. Prognosis of R/R DLBCL patients is poor, particularly for those eligible neither for chimeric antigen receptor (CAR) T-cell therapy nor autologous stem cell transplantation (ASCT), representing a significant unmet clinical need. The advent of bispecific monoclonal antibodies (BsAbs), such as bispecific T-cell engagers (BiTEs), dual affinity retargeting (DART) molecules and IgG-like bispecific antibodies, offers a novel promising therapeutic approach in the treatment of DLBCL, both as frontline treatment and in the R/R setting. BsAbs simultaneously engage two different antigens, a tumor-associated antigen and an immune cell antigen, redirecting T-cells against malignant cells and enhancing the immune response. Most BsAbs developed for the treatment of NHLs engage T-cells via CD3 and malignant B-cells via CD20, a surface antigen expressed on most lymphomatous cells. Engagement of malignant B-cells by BsAbs activates T-cells, leading to the release of multiple cytokines and potentially to two characteristic adverse events: cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). The most extensively studied BsAbs, in both the frontline and relapsed/refractory (R/R) settings, include epcoritamab, glofitamab, mosunetuzumab, and odronextamab. Epcoritamab and glofitamab have received FDA and EMA approval for R/R DLBCL after two or more systemic line of therapies. EMA has also approved glofitamab in combination with gemcitabine and oxaliplatin (GemOx) for patients with R/R DLBCL ineligible for ASCT, whereas this indication has not been approved by FDA. Odronextamab is approved by EMA for R/R DLBCL and FL in patients who have received at least two prior lines of therapy, but it has not been approved by FDA. Mosunetuzumab is approved by both agencies—but only for R/R follicular lymphoma (FL). BsAbs represent a breakthrough therapy in the treatment of DLBCL, especially in R/R diseases. The purpose of this article is to review the landscape of BsAbs in DLBCL.

Background and Clinical Significance: Mastocytosis and mast cell activation syndrome (MCAS) include conditions in which patients manifest signs, symptoms, and laboratory findings consistent with mast cell activation and can only be diagnosed in the presence of specific criteria. Mutations of ZRSR2, a gene involved in RNA splicing, are not closely associated with mast cell disorders, but rather with myelodysplastic syndromes development. Case Presentation: We report a case of a 37-year-old man who was referred to our institution for anaphylaxis after a bee sting and elevated serum tryptase levels (17.8 ng/mL in the first sample and 19.2 ng/mL in the second sample). Complete blood count was unremarkable. Bone marrow biopsy showed signs of dysplasia and some CD25+ mast cells. ASO-qPCR and targeted myeloid NGS analysis did not detect the KIT p.D816V mutation, but rather showed the presence of a pathogenetic variant of the ZRSR2 gene (p.S447_R448del) with a variant allele frequency of 7.4%. Mastocytosis could not be diagnosed based on the established diagnostic criteria. The patient’s symptoms were not recurrent and tryptase release was not event-related; therefore, a diagnosis of MCAS could not be made either. Taken together, these findings led to the diagnosis of clonal hematopoiesis of indeterminate potential (CHIP). A watch and wait strategy consisting of clinical evaluations, blood tests, and cardiovascular risk assessment was initiated. Conclusions: This case report highlights the importance of combining clinical and laboratory findings, hematopathology, and molecular analyses to establish the most probable diagnosis in challenging cases. It also underscores the possible relevance of identifying predisposing conditions, such as CHIP, in order to guide counseling and follow-up strategy.