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BACKGROUND: In a previous randomised EORTC study on adjuvant dibromodulcitol (DBD) and bichloroethylnitrosourea (BCNU) in adults with glioblastoma multiforme (GBM) and anaplastic astrocytoma (AA), a clinically significant trend towards a longer overall survival (OS) and a progression-free survival (PFS) was observed in the subgroup of AA. The aim of the present study was to test this adjuvant regimen in a larger number of AA patients. METHODS: Continuation of the previous phase III trial for newly diagnosed AA according to the local pathologist. Patients were randomised to either radiotherapy only or to radiotherapy in combination with BCNU on day 2 and weekly DBD, followed by adjuvant DBD and BCNU in cycles of six weeks for a maximum total treatment duration of one year. OS was the primary end-point. RESULTS: Patients (193 ) with newly diagnosed AA according to local pathological assessment were randomised to radiotherapy (RT) alone (n=99), or to RT plus DBD/BCNU (n=94); 12 patients were considered not eligible. At central pathology review, over half (53%) of the locally diagnosed AA cases could not be confirmed. On intent-to-treat analysis, no statistically significant differences in OS (p=0.111) and PFS (p=0.087) were observed, median OS after RT was only 23.9 months 95% confidence interval (CI), [18.4-34.0] after RT plus DBD/BCNU 27.3 months 95% CI [21.4-46.8]. CONCLUSION: No statistically significant improvement in survival was observed after BCNU/DBD adjuvant chemotherapy in AA patients. The trend towards improved survival is consistent with previous reports. Central pathology review of grade 3 tumours remains crucial. [ABSTRACT FROM AUTHOR]

Background: A randomised controlled trial of radiotherapy alone versus radiotherapy with concomitant and adjuvant temozolomide for patients with glioblastoma showed that survival was higher for patients assigned combination treatment compared with those assigned standard radiotherapy alone. This paper reports the health-related quality of life (HRQOL) of the patients in this trial.Methods: 573 patients with newly diagnosed glioblastoma were randomly allocated either radiotherapy alone or radiotherapy and temozolomide. The primary endpoint was survival, and HRQOL was a secondary endpoint. We assessed HRQOL at baseline and at every 3 months during treatment until progression using the European Organisation for Research and Treatment of Cancer (EORTC) quality of life questionnaire core-30 (QLQ-C30) and the EORTC brain cancer module (EORTC BN-20). We calculated changes from baseline score for seven predefined HRQOL measures (fatigue, overall health, social function, emotional function, future uncertainty, insomnia, and communication deficit) and differences between groups for these measures at every time point. The significance of, and proportions of patients with, improved HRQOL scores--defined as a change of 10 points or more--were recorded. This trial is registered on the US National Cancer Institute website http://www.cancer.gov/search/NewClinicalTrials, NCT00006353.Findings: Baseline questionnaires were available for 490 (86%) patients. Baseline HRQOL scores did not differ between groups. At first follow-up, groups differed only in social functioning, favouring the radiotherapy-only group (mean score 79.0 [SD 3.2] for patients assigned radiotherapy vs 67.4 [2.7] for those assigned radiotherapy and temozolomide; difference between groups 11.6 points [95% CI 3.5-19.7], p=0.0052). Over subsequent assessments, HRQOL was much the same between treatment groups.Interpretation: Addition of temozolomide during and after radiotherapy for patients with newly diagnosed glioblastoma significantly improved survival without a negative effect on HRQOL. [ABSTRACT FROM AUTHOR]

Background and Purpose: CNS embryonal tumor with PLAGL1/PLAGL2 amplification (ET, PLAGL) is a newly identified, highly malignant pediatric tumor. Systematic MRI descriptions of ET, PLAGL are currently lacking., Materials and Methods: MRI data from 19 treatment-naïve patients with confirmed ET, PLAGL were analyzed. Evaluation focused on anatomical involvement, tumor localization, MRI signal characteristics, DWI behavior, and the presence of necrosis and hemorrhage. Descriptive statistics (median, interquartile range, percentage) were assessed., Results: Ten patients had PLAGL1 and nine PLAGL2 amplifications. The solid components of the tumors were often multinodular with heterogeneous enhancement (mild to intermediate in 47% and intermediate to strong in 47% of cases). Non-solid components included cysts in 47% and necrosis in 84% of the cases. The tumors showed heterogeneous T2WI hyper-and isointensity (74%), relatively little diffusion restriction (ADC values < contralateral normal-appearing WM in 36% of cases with available DWI), and tendencies towards hemorrhage/calcification (42%). No reliable distinction was found between PLAGL1- and PLAGL2- amplified tumors or compared to other embryonal CNS tumors., Conclusions: The study contributes to understanding the imaging characteristics of ET, PLAGL. It underscores the need for collaboration in studying rare pediatric tumors and advocates for the use of harmonized imaging protocols for better characterization., Abbreviations: ATRT= atypical teratoid/rhabdoid tumor; ETMR= embryonal tumor with multilayered rosettes; ET, PLAGL= CNS embryonal tumor with PLAGL amplification; EVD= external ventricular drain; IQR: interquartile range; PLAGL1= pleomorphic adenoma gene-like 1; PLAGL2= pleomorphic adenoma gene-like 2; WHO= World Health Organization., Competing Interests: Disclosure of potential conflicts of interest: Where authors are identified as personnel of the IARC/WHO, the authors alone are responsible for the views expressed in this article and they do not necessarily represent the decisions, policy, or views of the IARC/WHO. Zapotocky M: travel grant and advisory board AstraZeneca, (© 2024 by American Journal of Neuroradiology.)

Quiescence, a reversible state of cell-cycle arrest, is an important state during both normal development and cancer progression. For example, in glioblastoma (GBM) quiescent glioblastoma stem cells (GSCs) play an important role in re-establishing the tumour, leading to relapse. While most studies have focused on identifying differentially expressed genes between proliferative and quiescent cells as potential drivers of this transition, recent studies have shown the importance of protein oscillations in controlling the exit from quiescence of neural stem cells. Here, we have undertaken a genome-wide bioinformatic inference approach to identify genes whose expression oscillates and which may be good candidates for controlling the transition to and from the quiescent cell state in GBM. Our analysis identified, among others, a list of important transcription regulators as potential oscillators, including the stemness gene SOX2, which we verified to oscillate in quiescent GSCs. These findings expand on the way we think about gene regulation and introduce new candidate genes as key regulators of quiescence., (© 2024. The Author(s).)

Background: MR image classification in datasets collected from multiple sources is complicated by inconsistent and missing DICOM metadata. Therefore, we aimed to establish a method for the efficient automatic classification of MR brain sequences., Methods: Deep convolutional neural networks (DCNN) were trained as one-vs-all classifiers to differentiate between six classes: T1 weighted (w), contrast-enhanced T1w, T2w, T2w-FLAIR, ADC, and SWI. Each classifier yields a probability, allowing threshold-based and relative probability assignment while excluding images with low probability (label: unknown, open-set recognition problem). Data from three high-grade glioma (HGG) cohorts was assessed; C1 (320 patients, 20,101 MRI images) was used for training, while C2 (197, 11,333) and C3 (256, 3522) were for testing. Two raters manually checked images through an interactive labeling tool. Finally, MR-Class' added value was evaluated via radiomics model performance for progression-free survival (PFS) prediction in C2, utilizing the concordance index (C-I)., Results: Approximately 10% of annotation errors were observed in each cohort between the DICOM series descriptions and the derived labels. MR-Class accuracy was 96.7% [95% Cl: 95.8, 97.3] for C2 and 94.4% [93.6, 96.1] for C3. A total of 620 images were misclassified; manual assessment of those frequently showed motion artifacts or alterations of anatomy by large tumors. Implementation of MR-Class increased the PFS model C-I by 14.6% on average, compared to a model trained without MR-Class., Conclusions: We provide a DCNN-based method for the sequence classification of brain MR images and demonstrate its usability in two independent HGG datasets.

Purpose: This study investigates the impact of different intensity normalization (IN) methods on the overall survival (OS) radiomics models' performance of MR sequences in primary (pHGG) and recurrent high-grade glioma (rHGG)., Methods: MR scans acquired before radiotherapy were retrieved from two independent cohorts (rHGG C1: 197, pHGG C2: 141) from multiple scanners (15, 14). The sequences are T1 weighted (w), contrast-enhanced T1w (T1wce), T2w, and T2w-FLAIR. Sequence-specific significant features (SF) associated with OS, extracted from the tumour volume, were derived after applying 15 different IN methods. Survival analyses were conducted using Cox proportional hazard (CPH) and Poisson regression (POI) models. A ranking score was assigned based on the 10-fold cross-validated (CV) concordance index (C-I), mean square error (MSE), and the Akaike information criterion (AICs), to evaluate the methods' performance., Results: Scatter plots of the 10-CV C-I and MSE against the AIC showed an impact on the survival predictions between the IN methods and MR sequences (C1/C2 C-I range: 0.62-0.71/0.61-0.72, MSE range: 0.20-0.42/0.13-0.22). White stripe showed stable results for T1wce (C1/C2 C-I: 0.71/0.65, MSE: 0.21/0.14). Combat (0.68/0.62, 0.22/0.15) and histogram matching (HM, 0.67/0.64, 0.22/0.15) showed consistent prediction results for T2w models. They were also the top-performing methods for T1w in C2 (Combat: 0.67, 0.13; HM: 0.67, 0.13); however, only HM achieved high predictions in C1 (0.66, 0.22). After eliminating IN impacted SF using Spearman's rank-order correlation coefficient, a mean decrease in the C-I and MSE of 0.05 and 0.03 was observed in all four sequences., Conclusion: The IN method impacted the predictive power of survival models; thus, performance is sequence-dependent.

Lung cancer is the leading cause of cancer-related deaths worldwide, with non-small cell lung cancer (NSCLC) being the predominant histological subtype. Despite the emergence of targeted and immune-based therapies that have considerably improved the clinical outcomes of selected patients, the overall NSCLC survival rate remains poor. NSCLC patients experience clinical relapse mainly because of chemoresistance. One promising therapeutic approach is targeting specific molecular vulnerabilities that are associated with the metabolic reprogramming of cancer cells. This strategy relies on evidence that cancer cells rewire their metabolism to sustain their uncontrolled growth as well as invasive and metastatic properties, promoting adaptive resistance to chemo-radiotherapy. A critical component of this malignant transformation is the increased dependency on high levels of heat shock proteins (HSPs), which support the elevated protein folding demand and quality control of misfolded oncoproteins. Here, we provide an overview of the literature on metabolism reprogramming, deregulation of mitochondrion and on the role of HSPs in promoting malignancy in lung and other cancer types. A particular focus is dedicated to the role of mitochondrial HSP60 (HSPD1) in NSCLC metabolism and drug resistance for the potential development of new resistance-defying anti-HSP drugs., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The development of clinical trials has led to substantial improvements in the prevention and treatment of many diseases, including brain cancer. Advances in medicine, such as improved surgical techniques, the development of new drugs and devices, the use of statistical methods in research, and the development of codes of ethics, have considerably influenced the way clinical trials are conducted today. In addition, methods from the broad field of artificial intelligence, such as radiomics, have the potential to considerably affect clinical trials and clinical practice in the future. Radiomics is a method to extract undiscovered features from routinely acquired imaging data that can neither be captured by means of human perception nor conventional image analysis. In patients with brain cancer, radiomics has shown its potential for the non-invasive identification of prognostic biomarkers, automated response assessment, and differentiation between treatment-related changes from tumour progression. Despite promising results, radiomics is not yet established in routine clinical practice nor in clinical trials. In this Viewpoint, the European Organization for Research and Treatment of Cancer Brain Tumour Group summarises the current status of radiomics, discusses its potential and limitations, envisions its future role in clinical trials in neuro-oncology, and provides guidance on how to address the challenges in radiomics., Competing Interests: Declaration of interests MW reports research grants from Apogenix and Quercis, and honoraria for lectures, advisory board participation, or consulting from Bayer, Medac, Merck EMD, Nerviano Medical Sciences, Novartis, Orbus, Philogen, and y-mAbs. MP reports honoraria for lectures, consultation, or advisory board participation from Bayer, Bristol-Myers Squibb, Novartis, Gerson Lehrman Group, CMC Contrast, GlaxoSmithKline, Mundipharma, Roche, British Medical Journals, MedMedia, AstraZeneca, AbbVie, Lilly, Medahead, Daiichi Sankyo, Sanofi, Merck Sharp & Dohme, Tocagen, Adastra, and Gan & Lee Pharmaceuticals. MS reports speaker fees from AuntMinnie paid to their institution. All other authors declare no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Background: The identification of novel targets is of paramount importance to develop more effective drugs and improve the treatment of non-small cell lung cancer (NSCLC), the leading cause of cancer-related deaths worldwide. Since cells alter their metabolic rewiring during tumorigenesis and along cancer progression, targeting key metabolic players and metabolism-associated proteins represents a valuable approach with a high therapeutic potential. Metabolic fitness relies on the functionality of heat shock proteins (HSPs), molecular chaperones that facilitate the correct folding of metabolism enzymes and their assembly in macromolecular structures., Methods: Gene fitness was determined by bioinformatics analysis from available datasets from genetic screenings. HSPD1 expression was evaluated by immunohistochemistry from formalin-fixed paraffin-embedded tissues from NSCLC patients. Real-time proliferation assays with and without cytotoxicity reagents, colony formation assays and cell cycle analyses were used to monitor growth and drug sensitivity of different NSCLC cells in vitro. In vivo growth was monitored with subcutaneous injections in immune-deficient mice. Cell metabolic activity was analyzed through extracellular metabolic flux analysis. Specific knockouts were introduced by CRISPR/Cas9., Results: We show heat shock protein family D member 1 (HSPD1 or HSP60) as a survival gene ubiquitously expressed in NSCLC and associated with poor patients' prognosis. HSPD1 knockdown or its chemical disruption by the small molecule KHS101 induces a drastic breakdown of oxidative phosphorylation, and suppresses cell proliferation both in vitro and in vivo. By combining drug profiling with transcriptomics and through a whole-genome CRISPR/Cas9 screen, we demonstrate that HSPD1-targeted anti-cancer effects are dependent on oxidative phosphorylation and validated molecular determinants of KHS101 sensitivity, in particular, the creatine-transporter SLC6A8 and the subunit of the cytochrome c oxidase complex COX5B., Conclusions: These results highlight mitochondrial metabolism as an attractive target and HSPD1 as a potential theranostic marker for developing therapies to combat NSCLC., (© 2021. The Author(s).)

Chaperonins play an important role in folding newly synthesized or translocated proteins in all organisms. The bacterial chaperonin GroEL has served as a model system for the understanding of these proteins. In comparison, its human homolog, known as mitochondrial heat shock protein family member D1 (HSPD1) is poorly understood. Here, we present the structure of HSPD1 in the apo state determined by cryo-electron microscopy (cryo-EM). Unlike GroEL, HSPD1 forms mostly single ring assemblies in the absence of co-chaperonin (HSPE1). Comparison with GroEL shows a rotation and increased flexibility of the apical domain. Together with published structures of the HSPD1/HSPE1 co-chaperonin complex, this work gives insight into the structural changes that occur during the catalytic cycle. This new understanding of HSPD1 structure and its rearrangements upon complex formation may provide new insights for the development of HSPD1-targeting treatments against a diverse range of diseases including glioblastoma., Competing Interests: The authors declare no conflicts of interest., (© 2020.)

Background: Patients with anaplastic glioma (AG) harboring an isocitrate dehydrogenase mutation have potential durable survival after intensity-modulated radiotherapy (IMRT) and chemotherapy. Understanding long-term functioning, and the factors that have an impact on later effects, is important for decision making., Methods: Consecutive patients with AG who received IMRT were reviewed with regard to 6 survivorship domains, including Eastern Cooperative Oncology Group (ECOG) performance status, Medical Research Council (MRC) neurological status, late toxicity, comorbidity, functional status (employment/driving), and psychosocial events. Assessments were performed at baseline before RT; at month +6; and at years +1, +3, and +5 after RT. The primary endpoints were ECOG at year +3 and employment at year +3., Results: A total of 146 patients were included, with a median follow-up of 5.1 years. The 6-year overall survival rate was 78.7% (95% CI, 71.1%-87.0%). Baseline ECOG performance status was 0 to 1 in 82.2% of patients but improved at year +1 (95.7%) and year +3 (97.2%). Employment rates at year +3 and year +5 were 70.1% and 76.5%, respectively, compared with 61.6% at baseline. Worse ECOG performance status at year +3 was related to the anaplastic astrocytoma subtype (P = .001), delayed RT (P = .081), multiple craniotomies performed before RT (P = .002), worse ECOG performance status before RT (P < .001), worse MRC neurological status before RT (P < .001), seizures (P = .038), neurocognitive disturbance (P < .001), and the presence of recurrent disease (P = .004). Absent or impaired employment at year +3 was found to be related to older age (P = .007), delayed timing of RT (P = .023), multiple craniotomies prior to RT (P = .005), worse ECOG performance status before RT (P < .001), worse MRC neurological status before RT (P < .001), and neurocognitive disturbance (P < .001)., Conclusions: Patients with AG with an isocitrate dehydrogenase mutation have the potential for prolonged survival. Functional status appears to be good in patients who are free of disease progression at 3 to 5 years after IMRT, with >95% of patients having high ECOG performance status and >75% being employed., (© 2019 American Cancer Society.)

The overall survival for patients with primary glioblastoma is very poor. Glioblastoma contains a subpopulation of glioma stem cells (GSC) that are responsible for tumour initiation, treatment resistance and recurrence. PPARα is a transcription factor involved in the control of lipid, carbohydrate and amino acid metabolism. We have recently shown that PPARα gene and protein expression is increased in glioblastoma and has independent clinical prognostic significance in multivariate analyses. In this work, we report that PPARα is overexpressed in GSC compared to foetal neural stem cells. To investigate the role of PPARα in GSC, we knocked down its expression using lentiviral transduction with short hairpin RNA (shRNA). Transduced GSC were tagged with luciferase and stereotactically xenografted into the striatum of NOD-SCID mice. Bioluminescent and magnetic resonance imaging showed that knockdown (KD) of PPARα reduced the tumourigenicity of GSC in vivo. PPARα-expressing control GSC xenografts formed invasive histological phenocopies of human glioblastoma, whereas PPARα KD GSC xenografts failed to establish viable intracranial tumours. PPARα KD GSC showed significantly reduced proliferative capacity and clonogenic potential in vitro with an increase in cellular senescence. In addition, PPARα KD resulted in significant downregulation of the stem cell factors c-Myc, nestin and SOX2. This was accompanied by downregulation of the PPARα-target genes and key regulators of fatty acid oxygenation ACOX1 and CPT1A, with no compensatory increase in glycolytic flux. These data establish the aberrant overexpression of PPARα in GSC and demonstrate that this expression functions as an important regulator of tumourigenesis, linking self-renewal and the malignant phenotype in this aggressive cancer stem cell subpopulation. We conclude that targeting GSC PPARα expression may be a therapeutically beneficial strategy with translational potential as an adjuvant treatment. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland., (© 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.)

Organoid methodology provides a platform for the ex vivo investigation of the cellular and molecular mechanisms underlying brain development and disease. The high-grade brain tumor glioblastoma multiforme (GBM) is considered a cancer of unmet clinical need, in part due to GBM cell infiltration into healthy brain parenchyma, making complete surgical resection improbable. Modeling the process of GBM invasion in real time is challenging as it requires both tumor and neural tissue compartments. Here, we demonstrate that human GBM spheroids possess the ability to spontaneously infiltrate early-stage cerebral organoids (eCOs). The resulting formation of hybrid organoids demonstrated an invasive tumor phenotype that was distinct from noncancerous adult neural progenitor (NP) spheroid incorporation into eCOs. These findings provide a basis for the modeling and quantification of the GBM infiltration process using a stem-cell-based organoid approach, and may be used for the identification of anti-GBM invasion strategies.

Background: A critical challenge in the management of Glioblastoma Multiforme (GBM) tumors is the accurate diagnosis and assessment of tumor progression in a noninvasive manner. We have identified Membrane-type 1 matrix metalloproteinase (MT1-MMP) as an attractive biomarker for GBM imaging since this protein is actively involved in tumor growth and progression, correlates with tumor grade and is closely associated with poor prognosis in GBM patients. Here, we report the development of an immunoPET tracer for effective detection of MT1-MMP in GBM models., Methods: An anti-human MT1-MMP monoclonal antibody (mAb), LEM2/15, was conjugated to p-isothiocyanatobenzyl-desferrioxamine (DFO-NCS) for 89Zr labeling. Biodistribution and PET imaging studies were performed in xenograft mice bearing human GBM cells (U251) expressing MT1-MMP and non-expressing breast carcinoma cells (MCF-7) as negative control. Two orthotopic brain GBM models, patient-derived neurospheres (TS543) and U251 cells, with different degrees of blood-brain barrier (BBB) disruption were also used for PET imaging experiments., Results: 89Zr labeling of DFO-LEM2/15 was achieved with high yield (>90%) and specific activity (78.5 MBq/mg). Biodistribution experiments indicated that 89Zr-DFO-LEM2/15 showed excellent potential as a radiotracer for detection of MT1-MMP positive GBM tumors. PET imaging also indicated a specific and prominent 89Zr-DFO-LEM2/15 uptake in MT1-MMP+ U251 GBM tumors compared to MT1-MMP- MCF-7 breast tumors. Results obtained in orthotopic brain GBM models revealed a high dependence of a disrupted BBB for tracer penetrance into tumors. 89Zr-DFO-LEM2/15 showed much higher accumulation in TS543 tumors with a highly disrupted BBB than in U251 orthotopic model in which the BBB permeability was only partially increased. Histological analysis confirmed the specificity of the immunoconjugate in all GBM models., Conclusion: A new anti MT1-MMP-mAb tracer, 89Zr-DFO-LEM2/15, was synthesized efficiently. In vivo validation showed high-specific-contrast imaging of MT1-MMP positive GBM tumors and provided strong evidence for utility of MT1-MMP-targeted immunoPET as an alternate to nonspecific imaging of GBM.

As advances in the molecular and genetic profiling of pediatric medulloblastoma evolve, associations with prognosis and treatment are found (prognostic and predictive biomarkers) and research is directed at molecular therapies. Medulloblastoma typically affects young patients, where the implications of any treatment on the developing brain must be carefully considered. The aim of this article is to provide a clear comprehensible update on the role molecular profiling and subgroups in pediatric medulloblastoma as it is likely to contribute significantly toward prognostication. Knowledge of this classification is of particular interest because there are new molecular therapies targeting the Shh subgroup of medulloblastomas.

Standard treatment for the majority of malignant brain tumours consists of surgery and radiotherapy. This treatment has late morbidity which is accentuated in the very young child. As part of a strategy to improve quality of life and overall survival of young children with brain tumours, members of the United Kingdom Children's Cancer Study Group (UKCCSG) have piloted an intensive chemotherapy regimen which aims to avoid or delay radiotherapy following surgery. Twenty eight children with a variety of malignant brain tumours have received the regimen, which contains carboplatin, vincristine, cyclophosphamide, methotrexate, and cisplatin. The treatment is toxic, resulting in one death from infection. The bulk of the toxicity was associated with the administration of carboplatin. All but three children eventually required adjuvant radiotherapy and this was given between 1.5 and 27 months from diagnosis (median delay to radiotherapy, 12 months). Using this treatment regimen, overall survival at four years is 35% (confidence intervals 10% to 60%). While there is no evidence from this study that radiotherapy can be abandoned in the management of malignant brain tumours, its introduction may be delayed using suitable chemotherapy, thus allowing time for further CNS development. This treatment strategy has been taken forward as an international clinical trial run through the International Society for Paediatric Oncology, but using a smaller dose of carboplatin to reduce toxicity.

The antigenic characteristics of 20 primary cerebral lymphomas have been defined by their reactivity with a panel of monoclonal antibodies recognizing differentiation antigens of lymphocytes and other cell types. In 7 out of 20 cases (35%), immunohistological results were diagnostically crucial and this approach appeared almost to double the detection rate of brain lymphomas over a 10-year period. All 20 tumours were confirmed as B-cell neoplasms by the use of a monoclonal antibody (B-1) specific for B-lymphocytes, rather than by the demonstration of immunoglobulin production. Further immunophenotyping with antibody FMC7 indicated that the neoplastic B-cells had been 'arrested' at a relatively mature stage of differentiation. The importance of monoclonal antibody markers in the accurate diagnosis and characterization of primary cerebral lymphomas has now been established.