Combinatorial Single-Cell Analyses of Granulocyte-Monocyte Progenitor Heterogeneity Reveals an Early Uni-potent Neutrophil Progenitor.

Granulocyte-monocyte progenitors (GMPs) have been previously defined for their potential to generate various myeloid progenies such as neutrophils and monocytes. Although studies have proposed lineage heterogeneity within GMPs, it is unclear if committed progenitors already exist among these progenitors and how they may behave differently during inflammation. By combining single-cell transcriptomic and proteomic analyses, we identified the early committed progenitor within the GMPs responsible for the strict production of neutrophils, which we designate as proNeu1. Our dissection of the GMP hierarchy led us to further identify a previously unknown intermediate proNeu2 population. Similar populations could be detected in human samples. proNeu1s, but not proNeu2s, selectively expanded during the early phase of sepsis at the expense of monocytes. Collectively, our findings help shape the neutrophil maturation trajectory roadmap and challenge the current definition of GMPs.

iPS-cell-derived microglia promote brain organoid maturation via cholesterol transfer.

Microglia are specialized brain-resident macrophages that arise from primitive macrophages colonizing the embryonic brain1. Microglia contribute to multiple aspects of brain development, but their precise roles in the early human brain remain poorly understood owing to limited access to relevant tissues2-6. The generation of brain organoids from human induced pluripotent stem cells recapitulates some key features of human embryonic brain development7-10. However, current approaches do not incorporate microglia or address their role in organoid maturation11-21. Here we generated microglia-sufficient brain organoids by coculturing brain organoids with primitive-like macrophages generated from the same human induced pluripotent stem cells (iMac)22. In organoid cocultures, iMac differentiated into cells with microglia-like phenotypes and functions (iMicro) and modulated neuronal progenitor cell (NPC) differentiation, limiting NPC proliferation and promoting axonogenesis. Mechanistically, iMicro contained high levels of PLIN2+ lipid droplets that exported cholesterol and its esters, which were taken up by NPCs in the organoids. We also detected PLIN2+ lipid droplet-loaded microglia in mouse and human embryonic brains. Overall, our approach substantially advances current human brain organoid approaches by incorporating microglial cells, as illustrated by the discovery of a key pathway of lipid-mediated crosstalk between microglia and NPCs that leads to improved neurogenesis.

Developmental Analysis of Bone Marrow Neutrophils Reveals Populations Specialized in Expansion, Trafficking, and Effector Functions.

Neutrophils are specialized innate cells that require constant replenishment from proliferative bone marrow (BM) precursors as a result of their short half-life. Although it is established that neutrophils are derived from the granulocyte-macrophage progenitor (GMP), the differentiation pathways from GMP to functional mature neutrophils are poorly defined. Using mass cytometry (CyTOF) and cell-cycle-based analysis, we identified three neutrophil subsets within the BM: a committed proliferative neutrophil precursor (preNeu) which differentiates into non-proliferating immature neutrophils and mature neutrophils. Transcriptomic profiling and functional analysis revealed that preNeu require the C/EBPε transcription factor for their generation from the GMP, and their proliferative program is substituted by a gain of migratory and effector function as they mature. preNeus expand under microbial and tumoral stress, and immature neutrophils are recruited to the periphery of tumor-bearing mice. In summary, our study identifies specialized BM granulocytic populations that ensure supply under homeostasis and stress responses.

The impact of ischemia-reperfusion injuries on skin resident murine dendritic cells.

Pressure ulcers are a chronic problem for patients or the elderly who require extended periods of bed rest. The formation of ulcers is due to repeated cycles of ischemia-reperfusion (IR), which initiates an inflammatory response. Advanced ulcers disrupt the skin barrier, resulting in further complications. To date, the immunological aspect of skin IR has been understudied, partly due to the complexity of the skin immune cells. Through a combination of mass cytometry, confocal imaging and intravital multiphoton imaging, this study establishes a workflow for multidimensionality single cell analysis of skin myeloid cell responses in the context of IR injury with high spatiotemporal resolution. The data generated has provided us with previously uncharacterized insights into the distinct cellular behavior of resident dendritic cells (DCs) and recruited neutrophils post IR. Of interest, we observed a drop in DDC numbers in the IR region, which was subsequently replenished 48h post IR. More importantly, in these cells, we observe an attenuated response to repeated injuries, which may have implications in the subsequent wound healing process.

Aberrant immunoarchitecture distinguishes hyperplastic germinal centres in pattern 1 angioimmunoblastic T-cell lymphoma from reactive follicles.

We compare 30 biopsies each of Pattern 1 angioimmunoblastic T-cell lymphoma (AITL1) and reactive lymphoid hyperplasia (RLH) by immunohistology, in-situ hybridization for Epstein-Barr virus-encoded RNA and T-cell receptor-γ (TRG)-clonality. AITL1 cases, more often than RLH controls, were older [median ages 61 (range 23-79) vs 46 (range 11-59) years, p < 10(-4)], non-Chinese [16/30 (53%) vs 8/28 (29%), p = 0.035], presented nodally [29/30 (97%) vs 23/30 (77%), p = 0.024], showed: pan-T cell antigen attenuation [25/29 (86%) vs 5/21 (24%), p = 1.0 × 10(-5)], CD4 predominance [25/28 (89%) vs 12/23 (52%), p = 3.4 × 10(-3)], interfollicular lymphoid CD10-positivity [16/30 (53%) vs 1/29 (3%), p = 1.5 × 10(-5)], TRG clonality [16/28 (57%) vs 1/20 (5%), p = 1.4 × 10(-4)], higher maximum number of Epstein-Barr virus-encoded RNA + nuclei per 0.5-mm high-power field [median 6 (range 0-70) vs 1 (range 0-40), p = 0.012] and interfollicular Ki-67 proliferation fraction [median 40% (range 10-80%) vs 20% (range 5-40), p < 10(-4)], whereas their germinal centres (GCs) more often showed attenuation of CD10 [30/30 (100%) vs 11/29 (38%), p = 5.3 × 10(-8)] and CD57 [18/25 (72%) vs 4/22 (18%), p = 2.4 × 10(-4)] (respectively). GC-predominant PD-1 and ICOS immunoreactivity were more often seen in RLH [20/22 and 9/19 controls (91% and 47%)] than AITL1 [9/25 and 3/19 cases (36% and 16%), p = 1.0 × 10(-4) and 0.033, respectively]. Significant independent predictors against AITL1 were: solid GC CD10 immunoreactivity {p = 0.023, odds ratio (OR) for AITL1 0.01 [95% confidence interval (CI): 0.0002-0.529]}; lower interfollicular proliferation fraction [p = 0.047, OR for AITL1 1.1 (95% CI: 1.001-1.209) per % rise in Ki-67]; younger presenting age [p = 0.028, OR for AITL1 1.136 (95% CI: 1.014-1.272) per year older]. Hence, GCs and perifollicular zones in AITL1 are distinct from those in RLH.

Murine immunodeficiency virus-induced peripheral neuropathy and the associated cytokine responses.

Distal symmetrical polyneuropathy is the most common form of HIV infection-associated peripheral neuropathy and is often associated with pain. C57BL/6 (B6) mice infected with LP-BM5, a murine retroviral isolate, develop a severe immunodeficiency syndrome similar to that in humans infected with HIV-1, hence the term murine AIDS. We investigated the induction of peripheral neuropathy after LP-BM5 infection in B6 mice. Infected B6 mice, like HIV-infected humans, exhibited behavioral (increased sensitivity to mechanical and heat stimuli) and pathological (transient loss of intraepidermal nerve fibers) signs of peripheral neuropathy. The levels of viral gag RNA were significantly increased in all tissues tested, including spleen, paw skin, lumbar dorsal root ganglia, and lumbar spinal cord, postinfection (p.i.). Correlated with the development of peripheral neuropathy, the tissue levels of several cytokines, including IFN-γ, IL-1ß, IL-6, and IL-12, were significantly elevated p.i. These increases had cytokine-specific and tissue-specific profiles and kinetics. Further, treatment with the antiretroviral agent zidovudine either significantly reduced or completely reversed the aforementioned behavioral, pathologic, and cytokine changes p.i. These data suggest that LP-BM5 infection is a potential mouse model of HIV-associated distal symmetrical polyneuropathy that can be used for investigating the roles of various cytokines in infection-induced neuropathic pain. Further investigation of this model could give a better understanding of, and lead to more effective treatments for, HIV infection-associated painful peripheral neuropathy.

Effects of tonsillectomy on sleep study parameters in adult patients with obstructive sleep apnea--a prospective study.

OBJECTIVE: The objective of this study is to evaluate the efficacy of tonsillectomy in reduction of respiratory disturbance index (RDI) and other sleep study parameters in patients with obstructive sleep apnea (OSA). METHODS: This study involves 34 adults with OSA and Friedman grade 3 or 4 tonsils. All 34 patients were treated with tonsillectomy, as the only surgical treatment for OSA from 2007 to 2011. Pre- and postoperative polysomnography were performed in all these patients. RESULTS: Prior to tonsillectomy, 21 patients had severe, 9 had moderate, and 4 had mild OSA. Surgical response rate (defined as 50% or more reduction in apnea-hypopnea index (AHI) and a postoperative AHI of less than 20) was 71.4% among patients with severe OSA, 77.7% among patients with moderate, and 75% among patients with mild. Among all the 34 patients, there was a reduction of 24.6 (p = 0.000) in the RDI postoperatively. In our sub-analysis, we arbitrarily divided the patients into three groups: patients with RDI less than 30, patients with RDI between 30 and 60, and patients with RDI above 60. It showed that, in the group with RDI >60, an average reduction of RDI by 57.6 (p = 0.000) was achieved and was the greatest reduction in RDI. CONCLUSIONS: Tonsillectomy alone may be considered as an effective first line surgical procedure in the treatment of OSA in selected patients. Patients with Friedman grade 3 or 4 tonsils may be considered for tonsillectomy as the initial surgical procedure, reserving other upper airway procedures at a later stage if necessary.

Deterministic reprogramming of neutrophils within tumors.

Neutrophils are increasingly recognized as key players in the tumor immune response and are associated with poor clinical outcomes. Despite recent advances characterizing the diversity of neutrophil states in cancer, common trajectories and mechanisms governing the ontogeny and relationship between these neutrophil states remain undefined. Here, we demonstrate that immature and mature neutrophils that enter tumors undergo irreversible epigenetic, transcriptional, and proteomic modifications to converge into a distinct, terminally differentiated dcTRAIL-R1+ state. Reprogrammed dcTRAIL-R1+ neutrophils predominantly localize to a glycolytic and hypoxic niche at the tumor core and exert pro-angiogenic function that favors tumor growth. We found similar trajectories in neutrophils across multiple tumor types and in humans, suggesting that targeting this program may provide a means of enhancing certain cancer immunotherapies.

Timing and location dictate monocyte fate and their transition to tumor-associated macrophages.

Tumor-associated macrophages (TAMs) are a heterogeneous population of cells whose phenotypes and functions are shaped by factors that are incompletely understood. Herein, we asked when and where TAMs arise from blood monocytes and how they evolve during tumor development. We initiated pancreatic ductal adenocarcinoma (PDAC) in inducible monocyte fate-mapping mice and combined single-cell transcriptomics and high-dimensional flow cytometry to profile the monocyte-to-TAM transition. We revealed that monocytes differentiate first into a transient intermediate population of TAMs that generates two longer-lived lineages of terminally differentiated TAMs with distinct gene expression profiles, phenotypes, and intratumoral localization. Transcriptome datasets and tumor samples from patients with PDAC evidenced parallel TAM populations in humans and their prognostic associations. These insights will support the design of new therapeutic strategies targeting TAMs in PDAC.

Emotional Variance Analysis: A new sentiment analysis feature set for Artificial Intelligence and Machine Learning applications.

Sentiment Analysis (SA) is a category of data mining techniques that extract latent representations of affective states within textual corpuses. This has wide ranging applications from online reviews to capturing mental states. In this paper, we present a novel SA feature set; Emotional Variance Analysis (EVA), which captures patterns of emotional instability. Applying EVA on student journals garnered from an Experiential Learning (EL) course, we find that EVA is useful for profiling variations in sentiment polarity and intensity, which in turn can predict academic performance. As a feature set, EVA is compatible with a wide variety of Artificial Intelligence (AI) and Machine Learning (ML) applications. Although evaluated on education data, we foresee EVA to be useful in mental health profiling and consumer behaviour applications. EVA is available at https://qr.page/g/5jQ8DQmWQT4. Our results show that EVA was able to achieve an overall accuracy of 88.7% and outperform NLP (76.0%) and SentimentR (58.0%) features by 15.8% and 51.7% respectively when predicting student experiential learning grade scores through a Multi-Layer Perceptron (MLP) ML model.

In Vitro Cytotoxicity of Antiresorptive and Antiangiogenic Compounds on Oral Tissues Contributing to MRONJ: Systematic Review.

BACKGROUND: Invasive dental treatment in patients exposed to antiresorptive and antiangiogenic drugs can cause medication-related osteonecrosis of the jaw (MRONJ). Currently, the exact pathogenesis of this disease is unclear. METHODS: In March 2022, Medline (Ovid), Embase (Ovid), Scopus, and Web of Science were screened to identify eligible in vitro studies investigating the effects of antiresorptive and antiangiogenic compounds on orally derived cells. RESULTS: Fifty-nine articles met the inclusion criteria. Bisphosphonates were used in 57 studies, denosumab in two, and sunitinib and bevacizumab in one. Zoledronate was the most commonly used nitrogen-containing bisphosphonate. The only non-nitrogen-containing bisphosphonate studied was clodronate. The most frequently tested tissues were gingival fibroblasts, oral keratinocytes, and alveolar osteoblasts. These drugs caused a decrease in cell proliferation, viability, and migration. CONCLUSIONS: Antiresorptive and antiangiogenic drugs displayed cytotoxic effects in a dose and time-dependent manner. Additional research is required to further elucidate the pathways of MRONJ.

Sun exposure and risk of lymphoid neoplasms in Singapore.

BACKGROUND: Epidemiologic studies have reported an inverse association between sun exposure and non-Hodgkin lymphoma (NHL), but these have been almost exclusively conducted in Western populations residing in temperate locations. We evaluated the association between personal outdoor sun exposure and risk of malignant lymphomas in Singapore. METHODS: A hospital-based case-control study of 541 incident cases of lymphoid neoplasms and 830 controls were recruited during 2004-2008. Participants were interviewed regarding recreational or occupational outdoor activities during childhood and in adulthood. Basic demographics and potential confounders were also collected. Odds ratios (OR) and 95 % confidence intervals (CI) were calculated using unconditional logistic regression analysis. RESULTS: Compared with individuals who did not have regular sun exposure, a lower risk of NHL was observed for those who reported regular exposure on non-school days during childhood [OR, 0.62; 95 % CI, 0.46-0.83] and non-working days in adulthood [OR, 0.70; 95 % CI, 0.51-0.97]. The protective effect was more evident among women. CONCLUSION: Our findings support an inverse relationship between intermittent sun exposure and the risk of NHL. These findings are consistent with the growing evidence from various countries, but further studies, especially prospective studies, are needed in Asian populations.

Does the proliferation fraction help identify mature B cell lymphomas with double- and triple-hit translocations?

AIMS: The entity 'B cell lymphoma, unclassifiable, with features intermediate between diffuse large B cell lymphoma (DLBCL) and Burkitt lymphoma (BL)' refers to B cell neoplasms that share overlapping characteristics of BL and DLBCL. A subset of these 'grey-zone lymphomas' possesses C-MYC and IGH translocations but, in addition, contains additional rearrangements of BCL2 and/or BCL6 genes. The aim of this study was to investigate if the proliferation fraction by Ki67 immunostaining can be used to identify such double-/triple-hit lymphomas. METHODS AND RESULTS: We studied 492 cases of mature aggressive B cell neoplasms by histology, immunohistochemistry and interphase fluorescence in-situ hybridization (FISH) using break-apart probes against C-MYC, BCL2, BCL6, IGH, MALT1, PAX5 and CCND1. Forty Burkitt lymphomas and 28 cases of MYC(+) double-/triple-hit lymphomas were identified. Of the latter, 77% and 54% displayed proliferation fractions exceeding 75% and 90%, respectively. With a cut-off of >75% by Ki67 immunostaining, the sensitivity and specificity for detection of MYC(+) double/triple translocations was 0.77 and 0.36. Raising the proliferation fraction criterion to >90% improved the specificity to 0.62 at the expense of a low sensitivity of 0.54. CONCLUSIONS: Immunostaining for Ki67 is not a useful approach to prescreen B cell lymphomas for MYC(+) double/triple translocations.

Angioimmunoblastic T-cell lymphoma with hyperplastic germinal centres (pattern 1) shows superior survival to patterns 2 and 3: a meta-analysis of 56 cases.

AIMS: Angioimmunoblastic T-cell lymphoma (AITL) may present in patterns 1, 2 or 3, representing those with hyperplastic, regressed or effaced germinal centres (GCs), respectively, but the prognostic utility of this subclassification has not been previously validated. METHODS AND RESULTS: Twenty-five cases of AITL were reviewed immunohistologically and with in-situ hybridization for Epstein-Barr virus-encoded RNA and polymerase chain reaction for T-cell receptor gamma and immunoglobulin heavy chain clonality and followed for up to 120 months. Four cases had conventional hyperplastic GCs, two had floral GCs, and one had progressively transformed GCs, consistent with pattern 1 and one additional case had hyalinized GCs, consistent with pattern 2. The remaining 17 (pattern 3) cases lacked morphologically discernible GCs. The Kaplan-Meier survival distribution of pattern 1 cases (5-year survival 83%) was superior to that of pattern 2 and 3 cases [5-year-survival 36% (P = 0.0417)] only when combined with the 31 cases, seven of which were pattern 1, that Attygalle et al. had followed for up to 247 months and previously published. Furthermore, the development of B-lineage (classical Hodgkin or diffuse large-cell) lymphoma was associated exclusively with pattern 3 (P = 0.0057). CONCLUSIONS: Pattern 1 represents an indolent phase/grade of AITL, unassociated with the development of secondary B-lineage lymphoma and uninfluenced by treatment regimen.

Transitional premonocytes emerge in the periphery for host defense against bacterial infections.

Circulating Ly6Chi monocytes often undergo cellular death upon exhaustion of their antibacterial effector functions, which limits their capacity for subsequent macrophage differentiation. This shrouds the understanding on how the host replaces the tissue-resident macrophage niche effectively during bacterial invasion to avert infection morbidity. Here, we show that proliferating transitional premonocytes (TpMos), an immediate precursor of mature Ly6Chi monocytes (MatMos), were mobilized into the periphery in response to acute bacterial infection and sepsis. TpMos were less susceptible to apoptosis and served as the main source of macrophage replenishment when MatMos were vulnerable toward bacteria-induced cellular death. Furthermore, TpMo and its derived macrophages contributed to host defense by balancing the proinflammatory cytokine response of MatMos. Consequently, adoptive transfer of TpMos improved the survival outcome of lethal sepsis. Our findings hence highlight a protective role for TpMos during bacterial infections and their contribution toward monocyte-derived macrophage heterogeneity in distinct disease outcomes.

Intravital Imaging of Bone Marrow Microenvironment in the Mouse Calvaria and Tibia.

The complex bone marrow microenvironment or niche is an important anatomical structure responsible for hematopoiesis and providing support to the immune cells function. Being the source of immune and blood cells, the interaction of these hematopoietic stem and progenitor cells with the cellular niches regulates their ability for self-renewal, proliferation, and differentiation. Dynamic imaging not only provides spatiotemporal information of cell motility but also the morphological changes due to cell-cell interactions in the bone marrow, providing insights into the ongoing physiological activities within the tissue. Here, we describe customized stages with compatible equipment best suited for the upright two-photon microscope, accompanied by detailed methods for both calvarial and tibial intravital imaging. We demonstrate a general protocol for calvarial imaging using a minimally invasive surgical approach, and introduce a bone shaving-based tibial imaging as a complementary method. To demonstrate the applicability of our method we used Lyz2-EGFP transgenic mice to track bone marrow neutrophil activities as an example.

Neutrophils in cancer-unresolved questions.

There is growing recognition that neutrophils play an important role in cancer initiation, progression and metastasis. Although they are typically characterized as short-lived effector cells, neutrophils have been shown to acquire immunosuppressive and pro-tumorigenic functions that promote tumor progression and escape. As such, inhibition of their function or depletion of neutrophils are being explored as potential cancer therapies. However, growing evidence of neutrophil diversification in cancer and their potential anti-tumor roles raise many unresolved questions. Here, we review recent advances that address the definition, origin and function of neutrophils in cancer, and elaborate on obstacles that make the study of neutrophils challenging. We envision that this review will provide the groundwork for focused design of therapeutics that will specifically target "tumorreprogrammed" neutrophils while sparing normal neutrophils to improve patient outcomes.

A Clinico-Genotypic Prognostic Index for De Novo Composite Diffuse Large B-Cell Lymphoma Arising from Follicular Lymphoma in Asian patients treated in the Rituximab Era.

Composite follicular lymphoma with diffuse large B-cell lymphoma (FL/DLBCL) is uncommonly found on lymph node biopsy and represents a rare haematological malignancy. We aim to examine clinico-pathological features of patients with FL/DLBCL and investigate predictors of survival outcome. We included in our retrospective study patients with histologically-proven FL/DLBCL at diagnosis (n = 106) and who were subsequently treated with rituximab-based chemoimmunotherapy from 2002-2017 at the National Cancer Centre. The cohort consisted of 34 women and 72 men with a median age of 59 years (range, 24-82). In a multivariate model inclusive of known clinico-pathological parameters at diagnosis, advanced stage (p = 0.0136), presence of MYC and/or BCL6 rearrangement (p = 0.0376) and presence of B symptoms (p = 0.0405) were independently prognostic for worse overall survival (OS). The only remaining independent prognostic variables for worse OS after including first-line treatment data in the model were use of chemotherapy regimens other than R-CHOP (p = 0.0360) and lack of complete response to chemotherapy (p < 0.0001) besides the presence of B symptoms (p = 0.0022). We generated a Clinico-Genotypic Index by point-wise addition of all five adverse parameters (score of 0-1, 2, 3, 4-5) which revealed four prognostic risk groups with a predicted 5-year OS of 100%, 62%, 40% and 0% (p < 0.0001) accounting for 50.0%, 24.5%, 18.9% and 6.6% of the cohort respectively. We propose that R-CHOP should be the recommended first-line regimen for composite FL/DLBCL.

MicroRNA-mediated down-regulation of PRDM1/Blimp-1 in Hodgkin/Reed-Sternberg cells: a potential pathogenetic lesion in Hodgkin lymphomas.

PRDM1/Blimp-1, a master regulator in terminal B-cell differentiation, has been recently identified as a tumor suppressor target for mutational inactivation in diffuse large B-cell lymphomas of the activated B-cell type. Our studies here demonstrate that PRDM1/blimp-1 is also a target for microRNA (miRNA)-mediated down-regulation by miR-9 and let-7a in Hodgkin/Reed-Sternberg (HRS) cells of Hodgkin lymphoma (HL). MiRNA expression profiling by direct miRNA cloning demonstrated that both of these miRNAs are among the most highly expressed in cultured HRS cells. These miRNAs functionally targeted specific binding sites in the 3' untranslated region of PRDM1/blimp-1 mRNA and repressed luciferase reporter activities through repression of translation. In addition, high levels of miR-9 and let-7a in HL cell lines correlated with low levels of PRDM1/Blimp-1. Similar to their in vitro counterparts, the majority of HRS cells in primary HL cases showed weak or no PRDM1/Blimp-1 expression. Over-expression of miR-9 or let-7a reduced PRDM1/Blimp-1 levels in U266 cells by 30% to 50%, whereas simultaneous inhibition of their activities in L428 cells resulted in an approximately 2.6-fold induction in PRDM1/Blimp-1. MiRNA-mediated down-regulation of PRDM1/Blimp-1 may contribute to the phenotype maintenance and pathogenesis of HRS cells by interfering with normal B-cell terminal differentiation, thus representing a novel molecular lesion, as well as a potential therapeutic target in HL.

Presence of a high-grade component in gastric mucosa-associated lymphoid tissue (MALT) lymphoma is not associated with an adverse prognosis.

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma and diffuse large B cell lymphoma (DLBCL) show a spectrum of disease characterized by varying proportions of low-grade and high-grade components. While the natural history and optimum treatment for low-grade gastric MALT lymphoma and DLBCL is well established, the prognosis and optimal treatment of patients with both low- and high-grade components is not well established. The purpose of our study was to evaluate the clinical characteristics, survival outcomes, and prognostic factors of patients with gastric MALT lymphoma and gastric DLBCL. A retrospective review of patients with gastric MALT lymphoma, gastric DLBCL, or MALT lymphoma with a high-grade component treated at our centers from 1994 to 2006 was performed. Patients were divided into three categories: "pure MALT lymphoma," "MALT lymphoma with high-grade component" (mixed), and "pure DLBCL." Seventy-six patients were included in our study-26 with pure MALT, 22 with MALT with high-grade component ("mixed"), and 28 with pure DLBCL. Pure MALT lymphoma and mixed lymphoma patients had similar clinical characteristics, whereas pure DLBCL patients had less favorable disease characteristics with significantly poorer performance status, higher number of extranodal sites of disease, higher stage, and larger proportion of bone marrow involvement and international prognostic index (IPI) scores compared with mixed lymphoma. The majority of mixed lymphoma (72.7%) and DLBCL patients (71.4%) were treated with chemotherapy. Of patients receiving chemotherapy, a higher proportion of mixed lymphoma and DLBCL patients received anthracycline-based combination chemotherapy regimens compared with MALT lymphoma (73% vs 71% vs 8%) whereas the proportion of mixed lymphoma and DLBCL patients was similar (p = 0.919). At a median follow-up of 37 months, the 5-year overall survival was 66.9%. The 5-year overall survival was 78% for MALT lymphoma, 84% for mixed lymphoma, and 45% for DLBCL. On univariate analysis, DLBCL histology, age, performance status, serum albumin, lactate dehydrogenase, bone marrow, number of extranodal sites, stage, and IPI score were prognostic for inferior survival. On multivariate analysis, DLBCL histology remained significantly prognostic for inferior survival, independent of chemotherapy regimen (hazard ratio (HR) 6.66, 95% confidence interval (CI) 2.01-21.41, p = 0.001). Mixed histology was not prognostic for inferior survival (HR 1.13, 95% CI 0.28-4.54, p = 0.868). Other factors prognostic for inferior survival were serum albumin <37 g/L (HR 3.22, 95% CI 1.11-13.22, p = 0.034) and treatment with non-cyclophosphamide, doxorubicin, vincristine, and prednisolone chemotherapy (HR 4.89, 95% CI 1.67-14.36, p = 0.004). In conclusion, the clinical characteristics of mixed histology MALT lymphoma are similar to low-grade MALT lymphoma and significantly different from pure DLBCL. The prognosis of mixed histology MALT lymphoma is significantly better than pure DLBCL, independent of IPI and chemotherapy regimen, and pure DLBCL histology is independently prognostic of inferior survival outcome.