Post-diagnosis serum 25-hydroxyvitamin D concentrations in women treated for breast cancer participating in a lifestyle trial in Italy.

OBJECTIVE: To report cross-sectionally serum levels of 25-hydroxyvitamin D [25(OH)D] in women living in Italy within 12 months from breast cancer (BC) diagnosis. METHODS: Baseline data were obtained from 394 women diagnosed with primary BC, enrolled from 2016 to 2019 in a lifestyle trial conducted in Italy. Subjects' characteristics were compared between two 25(OH)D concentrations (hypovitaminosis D<20 and ≥20 ng/mL) with the Chi-squared test or Fisher's exact test for small-expected counts. Using multiple logistic regression-adjusted models, we estimated odds ratios (ORs) of hypovitaminosis D with 95% confidence intervals (CIs) in the total sample and in the unsupplemented subgroup. RESULTS: Hypovitaminosis D was found in 39% of all subjects, 60% in unsupplemented subjects, and 10% in supplemented subjects. Increasing ORs of hypovitaminosis D were found with increasing body mass index, 25-30, >30, and ≥35 versus <25 kg/m2 (ORs: 2.50, 4.64, and 5.81, respectively, in the total cohort and ORs: 2.68, 5.38, and 7.08 in the unsupplemented); living in the most southern Italian region (OR 2.50, 95%CI 1.22-5.13); and with hypertriglyceridemia (OR 2.46; 95%CI 1.16-5.22), chemotherapy history (OR 1.86, 95%CI 1.03-3.38), and inversely with anti-estrogenic therapy (OR 0.43, 95%CI 0.24-0.75) in the total sample. CONCLUSIONS: Hypovitaminosis D in women recently diagnosed with BC and participating in a lifestyle trial in Italy was widespread and highest with obesity, hypertriglyceridemia, and chemotherapy use. Considering that hypovitaminosis D is a risk factor for lower efficacy of bone density treatments and possibly BC mortality, our results suggest the need to promptly address and treat vitamin D deficiency.

Continent-wide declines in shallow reef life over a decade of ocean warming.

Human society is dependent on nature1,2, but whether our ecological foundations are at risk remains unknown in the absence of systematic monitoring of species' populations3. Knowledge of species fluctuations is particularly inadequate in the marine realm4. Here we assess the population trends of 1,057 common shallow reef species from multiple phyla at 1,636 sites around Australia over the past decade. Most populations decreased over this period, including many tropical fishes, temperate invertebrates (particularly echinoderms) and southwestern Australian macroalgae, whereas coral populations remained relatively stable. Population declines typically followed heatwave years, when local water temperatures were more than 0.5 °C above temperatures in 2008. Following heatwaves5,6, species abundances generally tended to decline near warm range edges, and increase near cool range edges. More than 30% of shallow invertebrate species in cool latitudes exhibited high extinction risk, with rapidly declining populations trapped by deep ocean barriers, preventing poleward retreat as temperatures rise. Greater conservation effort is needed to safeguard temperate marine ecosystems, which are disproportionately threatened and include species with deep evolutionary roots. Fundamental among such efforts, and broader societal needs to efficiently adapt to interacting anthropogenic and natural pressures, is greatly expanded monitoring of species' population trends7,8.

Concussion education in medical students studying in Scotland: an assessment of knowledge and future needs.

BACKGROUND: Physicians play a key role in ensuring athletes with concussion safely return to sport. Research has shown deficiencies in concussion education amongst physicians and medical students. However, studies have not previously been conducted in UK medical schools. OBJECTIVES: To assess students' concussion knowledge and learning in Scottish Medical Schools. DESIGN: A survey with 23 questions was distributed to Year 3-6 medical students studying in Scotland in October 2020. The survey included the following: (1) demographics, (2) concussion knowledge, e.g. 'What is the role of headgear in preventing concussion?' (3) concussion learning, 'In which part of the curriculum should concussion be taught?.' Frequencies of responses were calculated for each question. RESULTS: 200 students responded (response rate 8%). The average symptoms and management score were 87.3% and 31% respectively. 15% of participants knew that headgear has no role in preventing concussions and one participant identified the minimum "return to sport" timeframes for adults and children. 15% had learnt about concussion at medical school with 92.5% interested in receiving concussion teaching at medical school. CONCLUSION: Knowledge gaps exist in managing and preventing sports-related concussion. There is a discrepancy between levels of concussion teaching and the desire and importance placed on concussion education.

Rugby Health and Well-Being Study: protocol for a UK-wide survey with health data cross-validation.

INTRODUCTION: Rugby football (Union and League) provides physical activity (PA) with related physical and mental health benefits. However, as a collision sport, rugby research and media coverage predominantly focus on injuries in elite players while the overall impact on health and well-being remains unclear. This study aims to provide a greater understanding of the risks and benefits of rugby participation in a diverse sample of men and women, current and former rugby Union and League players from recreational to the elite level of play. We will explore: (1) joint-specific injuries and concussion; (2) joint pain and osteoarthritis (OA); (3) medical and mental health conditions; (4) PA and sedentary behaviour and (5) well-being (quality of life, flourishing and resilience). METHODS AND ANALYSIS: The Rugby Health and Well-being Study is designed in two phases: (1) a UK-wide cross-sectional survey and (2) cross-validation using health register data from Scotland. Participants will be at least 16 years old, current or former rugby players who have played rugby for at least one season. We will report standardised, level of play-, sex- and age-stratified prevalence of joint injury, concussion, medical conditions and PA. We will describe injury/concussion prevention expectations and protective equipment use. Rugby-related factors associated with injury, pain, OA, PA, health and well-being will be explored in regression models. We will compare joint pain intensity and duration, elements of pain perception and well-being between recreational and elite players and further investigate these associations in regression models while controlling for confounding variables. In the second phase, we will validate self-reported with health register data, and provide further information on healthcare use. ETHICS AND DISSEMINATION: The Yorkshire and the Humber-Leeds East Research Ethics Committee (REC reference: 19/HY/0377) has approved this study (IRAS project ID 269424). The results will be disseminated through scientific publications, conferences and social media.

The relationships between rugby union, and health and well-being: a scoping review.

OBJECTIVE: To scope the relationships between rugby union, and health and well-being. DESIGN: Scoping review. DATA SOURCES: Published and unpublished reports of any age, identified by searching electronic databases, platforms and reference lists. METHODS: A three-step search strategy identified relevant published primary, secondary studies and grey literature, which were screened using a priori inclusion criteria. Data were extracted using a standardised tool, to form (1) a numerical analysis and (2) a thematic summary. RESULTS AND DISCUSSION: 6658 records were identified, and 198 studies met the inclusion criteria. All forms of rugby union can provide health-enhancing physical activity (PA). 'Non-contact' and wheelchair rugby in particular provide a wide range of physical and mental health and well-being benefits. The evidence is either mixed or unclear in relation to 'contact' rugby union and its effects on a range of physical health domains. Injury and concussion incidence rates are high for contact rugby union relative to other sports. CONCLUSIONS: A wide range of stakeholders as well as existing and potential participants can use this information to make a more informed decision about participating in and promoting rugby union as a health-enhancing activity. Industry and policy-makers can use this review to inform policies and strategies that look to increase participation rates and use rugby union as a vehicle to contribute positively to population health. Further research understanding rugby union's contribution to PA as well as to muscle-strengthening and balance is indicated, as well as research examining more health and well-being outcomes across more diverse cohorts.

Predictive Value of CD8 Expression and FoxP3 Methylation in Nasopharyngeal Carcinoma Patients Treated with Chemoradiotherapy in a Non-endemic Area.

Undifferentiated Nasopharyngeal Carcinoma (UNPC) is associated with Epstein-Barr Virus (EBV) and characterized by an abundant immune infiltrate potentially influencing the prognosis. Thus, we retrospectively assessed the significance of immunosuppression in the UNPC microenvironment as prognostic biomarker of treatment failure in a non-endemic area, and monitored the variation of systemic EBV-specific immunity before and after chemoradiotherapy (CRT). DNA and RNA were extracted from diagnostic biopsies obtained by tumor and adjacent mucosa from 63 consecutive EBV+ UNPC patients who underwent radical CRT. Among these patients 11 relapsed within 2 years. The expression of the EBV-derived UNPC-specific BARF1 gene and several immune-related genes was monitored through quantitative RT-PCR and methylation-specific PCR analyses. Peripheral T cell responses against EBV and BARF1 were measured in 14 patients (7 relapses) through IFN-γ ELISPOT assay. We found significantly higher expression levels of BARF1, CD8, IFN-γ, IDO, PD-L1, and PD-1 in UNPC samples compared to healthy tissues. CD8 expression was significantly reduced in both tumor and healthy tissues in UNPC patients who relapsed within two years. We observed a hypomethylated FOXP3 intron 1 exclusively in relapsed UNPC patients. Finally, we noticed a significant decrease in EBV- and BARF1-specific T-cells after CRT only in relapsing patients. Our data suggest that a high level of immunosuppression (low CD8, hypomethylated FoxP3) in UNPC microenvironment may predict treatment failure and may allow an early identification of patients who could benefit from the addition of immune modulating strategies to improve first line CRT.

Reference intervals for thyrotropin in an area of Northern Italy: the Pordenone thyroid study (TRIPP).

PURPOSE: Thyrotropin (TSH) is the most accurate marker of thyroid dysfunction in the absence of pituitary or hypothalamic disease. Studies on TSH reference intervals (RIs) showed wide inter-individual variability and prompted an intense debate about the best estimation of TSH RIs. DESIGN: We performed a population study on TSH RIs, using current data stored in the laboratory information system (LIS), at the Hospital Department of Laboratory Medicine, Pordenone (Italy), historically an area of mild-moderate iodine deficiency with a relatively high goiter prevalence. METHODS: 136,650 individuals constituted the final sample. A TSH immunoassay was performed on fasting serum samples with the Dimension Vista 1500 analyzer (Siemens Healthineers). We adopted the Kairisto's procedure to analyze TSH data downloaded by the LIS, applying the indirect strategy for deriving RIs. RESULTS: TSH RIs of the entire population were 0.32-3.36 mIU/L with a distribution skewed towards higher values. RIs were 0.26-3.61 mIU/L for females, and 0.32-3.01 mIU/L for males. Unlike other studies, TSH median levels progressively decreased from 0-4 to 85-104 years in the overall population, both in male and in female subgroups, showing an inverse correlation between TSH and age in all groups. CONCLUSIONS: This study is the first to analyze a high percentage (40%) of individuals from an ethnically homogenous Caucasian population. The results obtained emphasize the opportunity to define the TSH RIs according to age, gender and race, in addition to assay methods, and provide further insight about the possible role of iodine status.

Definition of the upper reference limit for thyroglobulin antibodies according to the National Academy of Clinical Biochemistry guidelines: comparison of eleven different automated methods.

PURPOSE: In the last two decades, thyroglobulin autoantibodies (TgAb) measurement has progressively switched from marker of thyroid autoimmunity to test associated with thyroglobulin (Tg) to verify the presence or absence of TgAb interference in the follow-up of patients with differentiated thyroid cancer. Of note, TgAb measurement is cumbersome: despite standardization against the International Reference Preparation MRC 65/93, several studies demonstrated high inter-method variability and wide variation in limits of detection and in reference intervals. Taking into account the above considerations, the main aim of the present study was the determination of TgAb upper reference limit (URL), according to the National Academy of Clinical Biochemistry guidelines, through the comparison of eleven commercial automated immunoassay platforms. METHODS: The sera of 120 healthy males, selected from a population survey in the province of Verona, Italy, were tested for TgAb concentration using eleven IMA applied on as many automated analyzers: AIA-2000 (AIA) and AIA-CL2400 (CL2), Tosoh Bioscience; Architect (ARC), Abbott Diagnostics; Advia Centaur XP (CEN) and Immulite 2000 XPi (IMM), Siemens Healthineers; Cobas 6000 (COB), Roche Diagnostics; Kryptor (KRY), Thermo Fisher Scientific BRAHMS, Liaison XL (LIA), Diasorin; Lumipulse G (LUM), Fujirebio; Maglumi 2000 Plus (MAG), Snibe and Phadia 250 (PHA), Phadia AB, Thermo Fisher Scientific. All assays were performed according to manufacturers' instructions in six different laboratories in Friuli-Venezia Giulia and Veneto regions of Italy [Lab 1 (AIA), Lab 2 (CL2), Lab 3 (ARC, COB and LUM), Lab 4 (CEN, IMM, KRY and MAG), Lab 5 (LIA) and Lab 6 (PHA)]. Since TgAb values were not normally distributed, the experimental URL (e-URL) was established at 97.5 percentile according to the non-parametric method. RESULTS: TgAb e-URLs showed a significant inter-method variability. Considering the same method, e-URL was much lower than that suggested by manufacturers (m-URL), except for ARC and MAG. Correlation and linear regression were unsatisfactory. Consequently, the agreement between methods was poor, with significant bias in Bland-Altman plot. CONCLUSIONS: Despite the efforts for harmonization, TgAb methods cannot be used interchangeably. Therefore, additional effort is required to improve analytical performance taking into consideration approved protocols and guidelines. Moreover, TgAb URL should be used with caution in the management of differentiated thyroid carcinoma patients since the presence and/or the degree of TgAb interference in Tg measurement has not yet been well defined.

Assessing National Biodiversity Trends for Rocky and Coral Reefs through the Integration of Citizen Science and Scientific Monitoring Programs.

Reporting progress against targets for international biodiversity agreements is hindered by a shortage of suitable biodiversity data. We describe a cost-effective system involving Reef Life Survey citizen scientists in the systematic collection of quantitative data covering multiple phyla that can underpin numerous marine biodiversity indicators at high spatial and temporal resolution. We then summarize the findings of a continental- and decadal-scale State of the Environment assessment for rocky and coral reefs based on indicators of ecosystem state relating to fishing, ocean warming, and invasive species and describing the distribution of threatened species. Fishing impacts are widespread, whereas substantial warming-related change affected some regions between 2005 and 2015. Invasive species are concentrated near harbors in southeastern Australia, and the threatened-species index is highest for the Great Australian Bight and Tasman Sea. Our approach can be applied globally to improve reporting against biodiversity targets and enhance public and policymakers' understanding of marine biodiversity trends.

Corrigendum: Assessing National Biodiversity Trends for Rocky and Coral Reefs through the Integration of Citizen Science and Scientific Monitoring Programs.

[This corrects the article DOI: 10.1093/biosci/biw180.].

Integrated polarization beam splitter with relaxed fabrication tolerances.

Polarization handling is a key requirement for the next generation of photonic integrated circuits (PICs). Integrated polarization beam splitters (PBS) are central elements for polarization management, but their use in PICs is hindered by poor fabrication tolerances. In this work we present a fully passive, highly fabrication tolerant polarization beam splitter, based on an asymmetrical Mach-Zehnder interferometer (MZI) with a Si/SiO(2) Periodic Layer Structure (PLS) on top of one of its arms. By engineering the birefringence of the PLS we are able to design the MZI arms so that sensitivities to the most critical fabrication errors are greatly reduced. Our PBS design tolerates waveguide width variations of 400nm maintaining a polarization extinction ratio better than 13dB in the complete C-Band.

Clinical multicenter evaluation of a new FXa-based Antithrombin assay.

INTRODUCTION: The determination of functional Antithrombin is a central part of thrombophilia screening. In this multicenter study, a new FXa-based method (INNOVANCE® Antithrombin) was evaluated on four different analyzers. METHODS: The INNOVANCE Antithrombin method was evaluated by precision and reference interval studies and by comparing the new method with established methods through parallel measurement of samples from 249 patients and 151 apparently healthy individuals. RESULTS: The INNOVANCE Antithrombin assay demonstrated on all analyzers repeatability coefficients of variation (CVs) ≤ 3.2% and within-device and between-run CVs ≤ 6.9%. The reference intervals of all analyzers are comparable with 2.5th percentiles between 80% and 85% of normal. The INNOVANCE Antithrombin and the FIIa-based Berichrom® AT III (A) methods demonstrated good concordance with correlation coefficients of r = 0.908 or higher. The INNOVANCE Antithrombin method demonstrated furthermore an excellent comparability with the STA® Antithrombin III assay and an acceptable comparability with the Coamatic® LR Antithrombin assay. The patients with congenital deficiency (n = 31) were identified with all assays except for the patients carrying the P41L heparin-binding site mutation, which was only identified with the INNOVANCE Antithrombin and the STA Antithrombin III methods. CONCLUSION: The INNOVANCE Antithrombin assay has high sensitivity for Antithrombin deficiencies and is reliable, precise and suitable for routine clinical use.

Early and short-term acenocumarine or dalteparin for the prevention of central vein catheter-related thrombosis in cancer patients: a randomized controlled study based on serial venographies.

BACKGROUND: We evaluated efficacy and safety of early and short-term prophylaxis with acenocumarine or dalteparin in the prevention of non-occlusive or occlusive central vein catheter-related thrombosis (CVCrT). PATIENTS AND METHODS: Consecutive cancer patients scheduled for chemotherapy randomly received: acenocumarine 1 mg/day for 3 days before and 8 days after central vein catheter (CVC) insertion; dalteparin 5000 IU 2 h before and daily for 8 days after CVC insertion; no anticoagulant treatment (NT). All patients underwent venography on days 8 and 30, some of them on days 90, 150 and 210 after CVC. RESULTS: A total of 450 patients were randomized, 348 underwent at least two venography. Both acenocumarine and dalteparin reduced venography-detected CVCrT rate [21.9% acenocumarine versus 52.6% NT, odds ratio (OR) 0.3, P < 0.01; 40% dalteparin versus 52.6% NT, OR 0.6, P = 0.05]. Acenocumarine was more effective than dalteparin (OR 0.4, P = 0.01). The rate of occlusive CVCrT was not different in the three groups (0.9% acenocumarine, 3.3% dalteparin, 1.8% NT; P = 0.40). Most CVCrTs (95.6%) were observed on day 8 after CVC insertion and were non-occlusive. CONCLUSIONS: In this study of early and short-term prophylaxis, acenocumarine was more effective than dalteparin on non-occlusive and asymptomatic CVCrT events. The first days following CVC insertion represent the highest risk for CVCrT.

MUC-1 (CA 15-3 antigen) as a highly reliable predictor of response to EGFR inhibitors in patients with bronchioloalveolar carcinoma: an experience on 26 patients.

BACKGROUND: Bronchioloalveolar carcinoma (BAC) is a histological subtype of non-small cell lung cancer (NSCLC), particularly of adenocarcinoma. Given its multifocality and the poor activity of chemotherapy, there is no established treatment for BAC, although promising results have been achieved with inhibitors of the epidermal growth factor receptor (EGFR). No tumor marker has been validated in the diagnosis and follow-up of lung cancer, in particular to predict the outcome of treatment with EGFR inhibitors. PURPOSE: As CA 15-3 antigen serum levels are reported to be pathologically abnormal in adenocarcinoma of the lung, we chose this tumor marker to monitor treatment with EGFR inhibitors of patients affected by adenocarcinoma with BAC features or pure BAC. PATIENTS AND METHODS: We collected data from 26 consecutive Caucasian patients with BAC, mostly women and never smokers, who received EGFR inhibitors. RESULTS: We noticed that all patients with normal CA 15-3 serum levels at baseline (15/26, 57.7%) showed a response to EGFR inhibitors, whereas all patients with abnormal CA 15-3 serum levels (11/26, 42.3%) did not. CONCLUSION: Our data suggest that CA 15-3 levels might be a predictive factor for the response to EGFR inhibitors in patients with BAC.

Pre-storage leucocyte depletion and transfusion reaction rates in cancer patients.

Passenger leucocytes transfused with allogenic blood are responsible for potential adverse effects. The impact of pre-storage leucodepletion (in-line filtration) of all whole blood units on transfusion reaction rate among patients suffering from cancer was retrospectively studied, comparing all reactions following red blood cell (RBC) transfusions during 2 years of pre-storage vs. 2 years of selective (bedside) leucodepletion. During selective leucodepletion, 5165 RBC units - of which 2745 were bedside filtered units- were transfused to 866 patients. Twenty-eight reactions were recorded: 22 (15 in the bedside group) febrile non-haemolytic transfusion reactions (FNHTR) and six allergic reactions (five in the bedside group). The overall percentage of reactions was 0.54 (0.76 for bedside) and 0.42 for FNHTR (0.54 for bedside). During pre-storage leucodepletion, 4116 RBC units were transfused to 841 patients. Eleven reactions were recorded: four FNHTR and seven allergic reactions (urticaria). The percentage of reactions for transfused RBC units was 0.26 (0.09 for FNHTR). Comparison between pre-storage filtration and bedside filtration with regard to FNHTR showed an odds ratio of 2.80 (95% confidence interval = 0.83-14.87) for bedside filtration. The study suggests that, for transfused patients affected by cancer, pre-storage leucodepletion is more effective than selective (bedside) filtration in reducing the incidence of transfusion reactions (FNHTR).

Ultrastructural observations in hepatitis C virus-infected lymphoid cells.

It is currently unclear whether the hepatocellular damage in chronic hepatitis C virus (HCV) infection is produced through the intrahepatic action of the anti-HCV immune response or through a direct cytopathic effect. In order to investigate the features of HCV replication (morphogenesis and cytopathic effect), we studied the infection of a permissive lymphocytic B cell line, Daudi cells, which were infected with sera of HCV-positive patients, and were examined after various time points under electron microscope. Viral genomic RNA was detected by in situ hybridization, and apoptosis with the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. The amount of viral genomic RNA was observed to increase during infection. HCV replicated rapidly, since characteristics of viral morphogenesis resembling those of yellow fever virus in a hepatoma cell line could be found 2 days after infection. These included the following: a) several viral particles identical in size (about 42 nm) and structure (a spherical 30-nm-sized electron-dense nucleocapsid surrounded by a membrane) to yellow fever virus were present in the cytoplasm of cells displaying already typical signs of the early stage of apoptosis; b) numerous membrane-bound organelles and in particular the endoplasmic reticulum and vacuoles were observed; c) proliferation of membranes was apparent; and d) intracytoplasmic electron-dense inclusion bodies which have been demonstrated to correspond to nucleocapsids for other flaviviruses were detected. Several cells presented electron-dense areas in the endoplasmic reticulum displaying 30-nm circular structures lying among an amorphous material. Striking cytopathic features with ballooning, extremely enlarged vacuoles and signs of apoptosis were found in cells often containing sequestered aggregates of virus-like particles. By in situ hybridization we found that such enlarged cells contained HCV RNA. Our results thus indicate that the ultrastructural features of HCV viral particles and their morphogenesis resemble that of yellow fever virus and dengue virus. In Daudi cells, HCV infection seems to rapidly trigger apoptotic cell death, and efficient release of viral particles does not seem to take place.

Plasma and platelet von Willebrand factor abnormalities in patients with uremia: lack of correlation with uremic bleeding.

Chronic renal failure often is associated with abnormal bleeding that may represent an important complication of this disorder. The hemorrhagic tendency currently is attributed to altered primary hemostasis, mainly platelet dysfunction. However, von Willebrand factor (vWF) also seems to be involved, even though the nature of its abnormalities is still controversial. To gain insight into the role of vWF in determining uremic bleeding, we studied 11 patients with stable, chronic renal failure. We found a significant increase in plasma factor VIII (FVIII), vWF:antigen (Ag), and vWF:ristocetin cofactor (Rco) levels, associated with a mean decrease in platelet vWF:Ag. Plasma vWF multimer pattern was characterized by increased representation of all oligomers in all patients, but five patients also showed a slight decrease in large vWF multimers. In addition, platelet vWF multimer pattern displayed a decrease in all components, especially those with high molecular weight. Despite normal bleeding time, collagen-induced platelet aggregation was defective in almost all patients, whereas vWF collagen binding capacity was normal. The levels of glycocalicin, the circulating fragment of glycoprotein Ib-IX, the major platelet vWF receptor, were also normal. In six patients who also were studied after initiation of dialysis, collagen-induced platelet aggregation was impaired further. Moreover, plasma vWF, and especially FVIII levels, were increased additionally, in association with a normalized platelet vWF content and an improved vWF multimer pattern. The results suggest that vWF abnormalities are present in uremia. Moreover, thrombopathy caused by impaired collagen-induced platelet aggregation is constantly present and apparently not improved by dialytic treatment.

Expression of MUM1/IRF4 selectively clusters with primary effusion lymphoma among lymphomatous effusions: implications for disease histogenesis and pathogenesis.

Primary effusion lymphoma (PEL) is a peculiar B-cell lymphoma characterized by infection by human herpesvirus type-8/Kaposi sarcoma-associated herpesvirus (HHV-8/KSHV) and by preferential growth in the serous body cavities. Histogenetic studies have suggested that PEL originates from B cells at a late stage of differentiation. In this study, we have investigated PEL for the expression status of MUM1/IRF4 (multiple myeloma 1/interferon regulatory factor 4) protein, which is involved in physiological B-cell maturation and represents a histogenetic marker of late B-cell differentiation. Using multiple detection assays, all cases of PEL (n = 22) were found to express MUM1/IRF4 molecules. MUM1/IRF4 expression was a selective feature of PEL among lymphomas involving the serous body cavities as secondary lymphomatous effusions generally failed to express the protein. In reactive lymphoid tissues, MUM1/ IRF4 expression clustered with advanced stages of B-cell differentiation. Comparison of MUM1/IRF4 expression with that of other histogenetic markers defined two phenotypic variants of PEL, i.e. MUM1/IRF4+, CD138/syndecan-1+, B-cell antigen- (20 out of 22 cases) and MUM1/IRF4+, CD138/syndecan-1-, B-cell antigen+ (2 out of 22 cases), suggesting a certain degree of heterogeneity in the disease histogenesis. The implications of these data are threefold. First, MUM1/IRF4 expression corroborates the notion that PEL originates from post-germinal centre, preterminally differentiated B-cells. Second, MUM1/IRF4 may help in the differential diagnosis of PEL among other lymphomas involving the serous body cavities. Finally, MUM1/IRF4 may interact with HHV-8/KSHV-encoded interferon regulatory factors (IRFs) and thus contribute to PEL escape from interferon-mediated control of viral infection.