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Oligodendroglioma, IDH-mutant and 1p/19q-codeleted has highly variable outcomes that are strongly influenced by patient age. The distribution of oligodendroglioma age is non-Gaussian and reportedly bimodal, which motivated our investigation of age-associated molecular alterations that may drive poorer outcomes. We found that elevated HOXD12 expression was associated with both older patient age and shorter survival in the TCGA (FDR < 0.01, FDR = 1e−5) and the CGGA (p = 0.03, p < 1e−3). HOXD12 gene body hypermethylation was associated with older age, higher WHO grade, and shorter survival in the TCGA (p < 1e−6, p < 0.001, p < 1e−3) and with older age and higher WHO grade in Capper et al. (p < 0.002, p = 0.014). In the TCGA, HOXD12 gene body hypermethylation and elevated expression were independently prognostic of NOTCH1 and PIK3CA mutations, loss of 15q, MYC activation, and standard histopathological features. Single-nucleus RNA and ATAC sequencing data showed that HOXD12 activity was elevated in neoplastic tissue, particularly within cycling and OPC-like cells, and was associated with a stem-like phenotype. A pan-HOX DNA methylation analysis revealed an age and survival-associated HOX-high signature that was tightly associated with HOXD12 gene body methylation. Overall, HOXD12 expression and gene body hypermethylation were associated with an older, atypically aggressive subtype of oligodendroglioma. [ABSTRACT FROM AUTHOR]

Purpose: To investigate whether qualitative and quantitative imaging phenotypes can predict the grade of oligodendroglioma. Methods: Retrospective chart and imaging reviews were conducted on 180 adults with oligodendroglioma (IDH-mutant and 1p/19q codeleted) between 2005 and 2021. Qualitative imaging characteristics including tumor location, calcification, gliomatosis cerebri, cystic change, necrosis, and infiltrative pattern were analyzed. Quantitative imaging assessment was performed from the tumor mask via automatic segmentation to calculate total, contrast-enhancing (CE), non-enhancing (NE), and necrotic tumor volumes. Logistic analyses were conducted to determine predictors of oligodendroglioma grade. Results: This study included 180 patients (84 [46.7%] with grade 2 and 96 [53.3%] with grade 3 oligodendrogliomas), with a median age of 42 years (range 23–76 years), comprising 91 females and 89 males. On univariable analysis, calcification (odds ratio [OR] = 6.00, P < 0.001), necrosis (OR = 21.84, P = 0.003), presence of CE tumor (OR = 7.86, P < 0.001), larger total (OR = 1.01, P < 0.001), larger CE (OR = 2.22, P = 0.010), and larger NE (OR = 1.01, P < 0.001) tumor volumes were predictors of grade 3 oligodendroglioma. On multivariable analysis, calcification (OR = 3.79, P < 0.001) and larger CE tumor volume (OR = 2.70, P = 0.043) remained as independent predictors of grade 3 oligodendroglioma. The multivariable model exhibited an AUC, accuracy, sensitivity, specificity of 0.78 (95% confidence interval 0.72–0.84), 72.8%, 79.2%, 69.1%, respectively. Conclusion: Presence of calcification and larger CE tumor volume may serve as useful imaging biomarkers for prediction of oligodendroglioma grade. Clinical Relevance Statement: Assessment of intratumoral calcification and CE tumor volume may facilitate accurate preoperative estimation of oligodendroglioma grade. Summary statement: Presence of intratumoral calcification and larger contrast-enhancing tumor volume were the significant predictors of higher grade oligodendroglioma based on the 2021 WHO classification. [ABSTRACT FROM AUTHOR]

Objective: Presurgical differentiation between astrocytomas and oligodendrogliomas remains an unresolved challenge in neuro-oncology. This research aims to provide a comprehensive understanding of each tumor's DSC-PWI signatures, evaluate the discriminative capacity of cerebral blood volume (CBV) and percentage of signal recovery (PSR) percentile values, and explore the synergy of CBV and PSR combination for pre-surgical differentiation. Methods: Patients diagnosed with grade 2 and 3 IDH-mutant astrocytomas and IDH-mutant 1p19q-codeleted oligodendrogliomas were retrospectively retrieved (2010–2022). 3D segmentations of each tumor were conducted, and voxel-level CBV and PSR were extracted to compute mean, minimum, maximum, and percentile values. Statistical comparisons were performed using the Mann-Whitney U test and the area under the receiver operating characteristic curve (AUC-ROC). Lastly, the five most discriminative variables were combined for classification with internal cross-validation. Results: The study enrolled 52 patients (mean age 45-year-old, 28 men): 28 astrocytomas and 24 oligodendrogliomas. Oligodendrogliomas exhibited higher CBV and lower PSR than astrocytomas across all metrics (e.g., mean CBV = 2.05 and 1.55, PSR = 0.68 and 0.81 respectively). The highest AUC-ROCs and the smallest p values originated from CBV and PSR percentiles (e.g., PSRp70 AUC-ROC = 0.84 and p value = 0.0005, CBVp75 AUC-ROC = 0.8 and p value = 0.0006). The mean, minimum, and maximum values yielded lower results. Combining the best five variables (PSRp65, CBVp70, PSRp60, CBVp75, and PSRp40) achieved a mean AUC-ROC of 0.87 for differentiation. Conclusions: Oligodendrogliomas exhibit higher CBV and lower PSR than astrocytomas, traits that are emphasized when considering percentiles rather than mean or extreme values. The combination of CBV and PSR percentiles results in promising classification outcomes. Clinical relevance statement: The combination of histogram-derived percentile values of cerebral blood volume and percentage of signal recovery from DSC-PWI enhances the presurgical differentiation between astrocytomas and oligodendrogliomas, suggesting that incorporating these metrics into clinical practice could be beneficial. Key Points: • The unsupervised selection of percentile values for cerebral blood volume and percentage of signal recovery enhances presurgical differentiation of astrocytomas and oligodendrogliomas. • Oligodendrogliomas exhibit higher cerebral blood volume and lower percentage of signal recovery than astrocytomas. • Cerebral blood volume and percentage of signal recovery combined provide a broader perspective on tumor vasculature and yield promising results for this preoperative classification. [ABSTRACT FROM AUTHOR]

• Adjuvant RT improved OS and PFS in patients with oligodendroglioma. • Earlier introduction of RT improved OS and PFS (i.e. adjuvant vs salvage). • Adjuvant RT improved OS in Grade 3 but not Grade 2 oligodendroglioma. • No significant differences in OS and PFS between adjuvant RT vs adjuvant chemotherapy alone. • In patients with low-risk features (e.g. Grade 2), alternative approaches such as adjuvant chemotherapy alone may be considered. Evidence and clinical guidelines support the use of adjuvant RT in high-risk low-grade gliomas. However, patients with oligodendroglioma have a more indolent disease course and delaying or avoiding RT is often considered to reduce treatment-related toxicities. As the optimal adjuvant management for oligodendroglioma is unclear, we aimed to assess the effect of adjuvant RT on overall survival (OS) and progression-free survival (PFS). MEDLINE, EMBASE, CENTRAL and CINAHL were searched from January 1990 to February 2023 for studies comparing adjuvant RT versus no adjuvant RT for patients with oligodendroglioma. This review found 17 eligible studies including 14 comparative retrospective studies and 3 randomized controlled trials. Using random-effects model, the results suggested that adjuvant RT improved OS by 28 % (HR 0.72, 95 % CI (0.56–0.93), I2 = 86 %), and PFS by 48 % (HR 0.52, (95 % CI 0.40–0.66), I2 = 48 %) compared to patients without adjuvant RT. Subgroup analysis showed that upfront adjuvant RT improved OS and PFS compared to salvage RT. There were no significant differences in OS and PFS between adjuvant RT versus adjuvant chemotherapy. There was improvement in PFS but not OS for adjuvant chemoradiotherapy versus adjuvant chemotherapy alone. Adjuvant RT improved OS in WHO Grade 3 but not WHO Grade 2 oligodendroglioma. Overall, adjuvant RT improved OS and PFS in patients with oligodendroglioma. In patients with low-risk features (e.g. Grade 2, gross total resection), alternative approaches and individualization of management such as adjuvant chemotherapy alone may be reasonable considering the lack of survival benefit. Future efforts should prospectively investigate these treatment regimens on molecularly-classified oligodendroglioma patients (defined by presence of IDH mutation and 1p/19q co-deletion), balancing between maximizing survival outcomes and reducing RT-related toxicities. [ABSTRACT FROM AUTHOR]

The 2021 World Health Organization (WHO) classification of the central nervous system (CNS) tumors has classified diffuse leptomeningeal glioneuronal tumor (DLGNT) as a mixed neuronal and glial tumor. Here, we report a DLGNT with two distinct morphological tumor components but identical molecular features. A four‐year‐old female child presented with progressive right upper extremity weakness. Magnetic resonance imaging (MRI) revealed the leptomeningeal enhancement over the brain stem and cervicothoracic spine. The histological examination of surgical specimens revealed two distinct tumor components: approximately half of the tumor is composed of oligodendroglioma‐like tumor intermingled with nodules of ganglioglioma‐like tumor. Immunohistochemistry confirmed the oligodendroglioma and ganglioglioma features. The molecular genetic studies demonstrated the features of DLGNT, including fusion of KIAA1549::BRAF, deletion of chromosome 1p, and absence of isocitrate dehydrogenase 1/2 (IDH1/2) mutation in both tumor components. Interestingly, the genetic studies also revealed the distinct chromosomal abnormalities of the loss of chromosome 4 only in oligodendroglioma‐like tumor and copy neutral loss of heterozygosity of 7Q34Q36.3 in the ganglioglioma‐like tumor component. This case highlights the critical role of molecular testing in the diagnosis of rare cases of DLGNT with diverse morphological components as well as in the identification of unique molecular alternations responsible for morphological phenotypes of the distinct tumors in DLGNT. [ABSTRACT FROM AUTHOR]

Background: Extraneural metastasis of central nervous system tumors is generally rare and most often reported in glioblastomas and medulloblastomas, whereas oligodendrogliomas seem to have the lowest risk of extracranial metastasis. Given its infrequent occurrence, both the diagnosis and therapy of metastatic oligodendroglioma is often challenging. Case presentation: This case study presents an oligodendroglioma, the isocitrate dehydrogenase 1 (IDH1) mutant, 1p/19q-codeleted tumor with bone marrow metastasis. The significance of this case lies in the comprehensive molecular analysis conducted for both the primary tumor and the metastasis. Chromosome 7 trisomy and chromosome 10 monosomy (+ 7/-10) were detected in the metastasis indicating molecular progression, which, to the best of our knowledge, has not been previously documented in metastatic oligodendroglioma. Conclusions: This case study serves additional information for better understanding of the metastatic capabilities of CNS tumors. [ABSTRACT FROM AUTHOR]

Objectives: Diagnosing brain tumors is critical due to their complex nature. This review explores the potential of in situ hybridization for diagnosing brain neoplasms, examining their attributes and applications in neurology and oncology. Methods: The review surveys literature and cross-references findings with the OMIM database, examining 513 records. It pinpoints mutations suitable for in situ hybridization and identifies common chromosomal and gene anomalies in brain tumors. Emphasis is placed on mutations’ clinical implications, including prognosis and drug sensitivity. Results: Amplifications in EGFR, MDM2, and MDM4, along with Y chromosome loss, chromosome 7 polysomy, and deletions of PTEN, CDKN2/p16, TP53, and DMBT1, correlate with poor prognosis in glioma patients. Protective genetic changes in glioma include increased expression of ADGRB3/1, IL12B, DYRKA1, VEGFC, LRRC4, and BMP4. Elevated MMP24 expression worsens prognosis in glioma, oligodendroglioma, and meningioma patients. Meningioma exhibits common chromosomal anomalies like loss of chromosomes 1, 9, 17, and 22, with specific genes implicated in their development. Main occurrences in medulloblastoma include the formation of isochromosome 17q and SHH signaling pathway disruption. Increased expression of BARHL1 is associated with prolonged survival. Adenomas mutations were reviewed with a focus on adenoma-carcinoma transition and different subtypes, with MMP9 identified as the main metalloprotease implicated in tumor progression. Discussion: Molecular-genetic diagnostics for common brain tumors involve diverse genetic anomalies. In situ hybridization shows promise for diagnosing and prognosticating tumors. Detecting tumor-specific alterations is vital for prognosis and treatment. However, many mutations require other methods, hindering in situ hybridization from becoming the primary diagnostic method. [ABSTRACT FROM AUTHOR]

In recent years, the classification of adult-type diffuse gliomas has undergone a revolution, wherein specific molecular features now represent defining diagnostic criteria of IDH-wild-type glioblastomas, IDH-mutant astrocytomas, and IDH-mutant 1p/19q-codeleted oligodendrogliomas. With the introduction of the 2021 WHO CNS classification, additional molecular alterations are now integrated into the grading of these tumors, given equal weight to traditional histologic features. However, there remains a great deal of heterogeneity in patient outcome even within these established tumor subclassifications that is unexplained by currently codified molecular alterations, particularly in the IDH-mutant astrocytoma category. There is also significant intercellular genetic and epigenetic heterogeneity and plasticity with resulting phenotypic heterogeneity, making these tumors remarkably adaptable and robust, and presenting a significant barrier to the design of effective therapeutics. Herein, we review the mechanisms and consequences of genetic and epigenetic instability, including chromosomal instability (CIN), microsatellite instability (MSI)/mismatch repair (MMR) deficits, and epigenetic instability, in the underlying biology, tumorigenesis, and progression of IDH-mutant astrocytomas. We also discuss the contribution of recent high-resolution transcriptomics studies toward defining tumor heterogeneity with single-cell resolution. While intratumoral heterogeneity is a well-known feature of diffuse gliomas, the contribution of these various processes has only recently been considered as a potential driver of tumor aggressiveness. CIN has an independent, adverse effect on patient survival, similar to the effect of histologic grade and homozygous CDKN2A deletion, while MMR mutation is only associated with poor overall survival in univariate analysis but is highly correlated with higher histologic/molecular grade and other aggressive features. These forms of genomic instability, which may significantly affect the natural progression of these tumors, response to therapy, and ultimately clinical outcome for patients, are potentially measurable features which could aid in diagnosis, grading, prognosis, and development of personalized therapeutics. [ABSTRACT FROM AUTHOR]

Simple Summary: PTEN is a critical tumor suppressor gene that plays a vital role in regulating cell proliferation, migration, and survival. The loss of PTEN function, either by genetic alterations or decreased protein expression, is frequent in human gliomas and has been correlated with tumor progression, grade, therapeutic resistance, and decreased overall survival in patients with glioma. This study investigates the immunohistochemical expression of PTEN in canine gliomas to evaluate possible alterations, as those reported in human gliomas. Our research demonstrates for the first time a variable reduction in PTEN protein expression in high-grade canine gliomas, particularly in astrocytomas. These observations are in line with those reported in human gliomas and provide a rationale for future studies regarding abnormalities in PTEN expression and PI3K/Akt/mTor pathway in canine gliomas, to evaluate its prognostic and therapeutic implications. Phosphatase and tensin homolog (PTEN) is a critical tumor suppressor gene with a vital role in regulating cell proliferation, migration, and survival. The loss of PTEN function, either by genetic alterations or decreased protein expression, is frequent in human gliomas and has been correlated with tumor progression, grade, therapeutic resistance, and decreased overall survival in patients with glioma. While different genetic mutations in PTEN gene have been occasionally reported in canine gliomas, no alterations in protein expression have been reported. This study investigates the immunohistochemical expression of PTEN in canine gliomas to evaluate possible alterations, as those reported in human gliomas. Immunohistochemical PTEN expression and pattern distribution were analyzed in 37 spontaneous canine gliomas. Among gliomas, 52.6% cases showed high PTEN expression and 48.6% displayed reduced (13.5%) or highly reduced (35.1%) immunopositivity. Most oligodendrogliomas showed high expression (73.7%), while the majority of astrocytomas (69.2%) showed a reduced or highly reduced expression. A reduced PTEN expression was mostly associated with a heterogeneous loss of PTEN immunopositivity. These observations are in line with those reported in human gliomas and provide a rationale for future studies regarding abnormalities in PTEN expression and PI3K/Akt/mTor pathway in canine gliomas, to evaluate its prognostic and therapeutic implications. [ABSTRACT FROM AUTHOR]

Gliomas are a kind of brain cancer that develops from glial cells. Glial cells provide nourishment and energy to nerve cells, and they also preserve the blood-brain barrier. A primary cancer of the central nervous system (CNS) is oligodendroglioma. This suggests that it originates in the brain or spinal cord. While oligodendrogliomas can strike anyone at any age, the age range of 35 to 44 is when they most commonly occur. Oligodendrogliomas are rare in young people and more common in men than women. Based on anecdotal data, patients with oligodendroglioma may present management challenges in Africa. There are delays in diagnosis and referrals due to the scarcity of neuroimaging facilities. A wide range of strategies have been put forth to improve pathology services in low- and middle-income nations. Adequate mentorship, short-term visitor programs, overcoming supply chain constraints, establishing training standards, and establishing the role of pathologists in cancer screening and early diagnosis have all been proposed as solutions to this problem. To sum up, oligodendroglioma is one of the low-grade gliomas this study looked at. Brain cancer is a serious public health concern in Africa. Improved options for screening and therapy are required to better address this problem. [ABSTRACT FROM AUTHOR]

Introduction: Concurrent primary brain tumors are rare clinical entities, with a prevalence ranging from 0.1 to 0.5% of all diagnosed brain tumors. The co-occurrence of meningioma and oligodendroglioma is particularly uncommon, posing unique diagnostic and therapeutic challenges. We describe the case of a patient diagnosed with concurrent meningioma and oligodendroglioma and review the existing literature on this rare phenomenon. Case Presentation: A 55-year-old female patient with a history of seizures presented to the emergency department with worsening headaches, nausea, and vomiting. She had a known right frontoparietal intracranial mass but had previously declined surgery. Magnetic resonance imaging revealed extensive fluid-attenuated inversion recovery /T2 hyperintensity around the lesion, which had slowly increased over 5 years; the growth of the lesion was producing a mass effect with a significant midline shift. The patient underwent urgent hemicraniectomy with subsequent resection. Clinical evaluation, imaging studies, and histopathological examination were conducted to confirm the diagnosis. Genetic and molecular analyses were also performed to explore potential underlying mechanisms. Histopathological findings confirmed a diagnosis of an isocitrate dehydrogenase-mutated World Health Organization Grade II oligodendroglioma with 1p/19q codeletion, along with a Grade I meningioma. Conclusion: The coexistence of meningioma and oligodendroglioma represents a rare clinical event. Surgical management remains the cornerstone of treatment. Further investigation into the genetic and environmental factors that contribute to the co-occurrence of such tumors could pave the way for more targeted therapeutic strategies. [ABSTRACT FROM AUTHOR]

Purpose: Oligodendrogliomas (ODGs) are a subtype of diffuse lower-grade gliomas with overall survival of > 10 years. This study aims to analyze long-term outcomes and identify prognostic factors in patients with WHO grade 2 ODG. Methods: We retrospectively reviewed 138 adult patients diagnosed with 1p/19q co-deleted ODG who underwent surgical resection or biopsy between 1994 and 2021, analyzing clinical data, treatment details, and outcomes. Progression-free survival (PFS) and overall survival (OS) were evaluated using Kaplan–Meier analysis. Univariate and multivariate Cox regression analyses were utilized to identify significant prognostic factors. Results: In the gross total resection (GTR) group, 63 (45.7%) underwent observation and 5 (3.6%) received postoperative treatment; in the non-GTR group, 37 (26.8%) were observed and 33 (23.9%) received postoperative treatment. The median PFS and OS were 6.8 and 18.4 years, respectively. Between adjuvant treatment and observation, there was no significant difference in PFS or OS. However, GTR or STR with less than 10% residual tumor exhibited significantly better PFS and OS compared to PR or biopsy (p = 0.022 and 0.032, respectively). Multivariate analysis revealed that contrast enhancement on MRI was associated with worse PFS (HR = 2.36, p < 0.001) and OS (HR = 5.89, p = 0.001). And the presence of seizures at presentation was associated with improved OS (HR = 0.28, p = 0.006). Conclusion: This study underscores favorable long-term outcomes for patients with 1p/19q co-deleted ODG WHO grade 2. Our findings indicate that the EOR plays a crucial role as a significant prognostic factor in enhancing PFS and OS outcomes in WHO grade 2 ODG. [ABSTRACT FROM AUTHOR]

Intraoperative magnetic resonance imaging (iMRI) is a powerful tool used to verify maximal safe resection of gliomas. However, unsuspected new or incidental findings can present difficult clinical scenarios. Here we present a case of a large supratentorial glioma resection where new, incidental bilateral cerebellar hemispheric enhancement was noted on iMRI. A 52-year-old male with a large intra-axial mass spanning the right temporal and parietal lobes underwent a craniotomy for tumor resection utilizing iMRI. Imaging displayed new, remote, bilateral cerebellar enhancement. Upon completion of surgery, the patient was extubated and was at his neurological baseline. An immediate CT scan showed no abnormalities in the cerebellum, and the duration of his hospital stay was unaffected by this finding. An MRI 24 hours after the procedure demonstrated complete resolution of the enhancement. New, remote contrast enhancement in the cerebellum raises concerns for the potentially emergent, well-defined pathology known as remote cerebellar hemorrhage (RCH). However, here we describe a case where these findings turned out to be clinically insignificant, CT-negative, and self-limiting. Therefore, here we call this finding remote non-hemorrhagic cerebellar contrast enhancement (RNHCCE) to differentiate it from RCE, and we discuss nuances and management considerations for differentiating the two.

Abstract Background Extraneural metastasis of central nervous system tumors is generally rare and most often reported in glioblastomas and medulloblastomas, whereas oligodendrogliomas seem to have the lowest risk of extracranial metastasis. Given its infrequent occurrence, both the diagnosis and therapy of metastatic oligodendroglioma is often challenging. Case presentation This case study presents an oligodendroglioma, the isocitrate dehydrogenase 1 (IDH1) mutant, 1p/19q-codeleted tumor with bone marrow metastasis. The significance of this case lies in the comprehensive molecular analysis conducted for both the primary tumor and the metastasis. Chromosome 7 trisomy and chromosome 10 monosomy (+ 7/-10) were detected in the metastasis indicating molecular progression, which, to the best of our knowledge, has not been previously documented in metastatic oligodendroglioma. Conclusions This case study serves additional information for better understanding of the metastatic capabilities of CNS tumors.

Introduction: Concurrent primary brain tumors are rare clinical entities, with a prevalence ranging from 0.1 to 0.5% of all diagnosed brain tumors. The co-occurrence of meningioma and oligodendroglioma is particularly uncommon, posing unique diagnostic and therapeutic challenges. We describe the case of a patient diagnosed with concurrent meningioma and oligodendroglioma and review the existing literature on this rare phenomenon. Case Presentation: A 55-year-old female patient with a history of seizures presented to the emergency department with worsening headaches, nausea, and vomiting. She had a known right frontoparietal intracranial mass but had previously declined surgery. Magnetic resonance imaging revealed extensive fluid-attenuated inversion recovery /T2 hyperintensity around the lesion, which had slowly increased over 5 years; the growth of the lesion was producing a mass effect with a significant midline shift. The patient underwent urgent hemicraniectomy with subsequent resection. Clinical evaluation, imaging studies, and histopathological examination were conducted to confirm the diagnosis. Genetic and molecular analyses were also performed to explore potential underlying mechanisms. Histopathological findings confirmed a diagnosis of an isocitrate dehydrogenase-mutated World Health Organization Grade II oligodendroglioma with 1p/19q codeletion, along with a Grade I meningioma. Conclusion: The coexistence of meningioma and oligodendroglioma represents a rare clinical event. Surgical management remains the cornerstone of treatment. Further investigation into the genetic and environmental factors that contribute to the co-occurrence of such tumors could pave the way for more targeted therapeutic strategies.

Abstract Purpose Oligodendrogliomas (ODGs) are a subtype of diffuse lower-grade gliomas with overall survival of > 10 years. This study aims to analyze long-term outcomes and identify prognostic factors in patients with WHO grade 2 ODG. Methods We retrospectively reviewed 138 adult patients diagnosed with 1p/19q co-deleted ODG who underwent surgical resection or biopsy between 1994 and 2021, analyzing clinical data, treatment details, and outcomes. Progression-free survival (PFS) and overall survival (OS) were evaluated using Kaplan–Meier analysis. Univariate and multivariate Cox regression analyses were utilized to identify significant prognostic factors. Results In the gross total resection (GTR) group, 63 (45.7%) underwent observation and 5 (3.6%) received postoperative treatment; in the non-GTR group, 37 (26.8%) were observed and 33 (23.9%) received postoperative treatment. The median PFS and OS were 6.8 and 18.4 years, respectively. Between adjuvant treatment and observation, there was no significant difference in PFS or OS. However, GTR or STR with less than 10% residual tumor exhibited significantly better PFS and OS compared to PR or biopsy (p = 0.022 and 0.032, respectively). Multivariate analysis revealed that contrast enhancement on MRI was associated with worse PFS (HR = 2.36, p

Magnetic resonance imaging (MRI) is an indispensable tool in neurosurgery, though it sometimes faces challenges such as “tumor mimicry.” While intraoperative MRI (iMRI) is widely recognized for its usefulness in achieving maximal safe resection during glioma surgery, instances of tumor mimicry still occur on iMRI. Moreover, reports on tumor mimics observed through iMRI, particularly in low-grade gliomas, remain scarce. In this article, we present a case of oligodendroglioma, where a newly emerged T2 high-signal intensity region on iMRI necessitated differentiation from tumor expansion.A 23-year-old man presented with a newly diagnosed brain tumor and underwent surgical removal. An iMRI taken after tumor removal revealed a newly emerged T2 hyperintense area without diffusion restriction around the resection cavity, which was not observed in the preoperative MRI. Suspecting residual tumor, we performed additional resection. An MRI on the following day confirmed that the T2 hyperintense area identified on the iMRI had been completely resected but also revealed an enlarged T2 high-signal area over a wider region. Histopathology found no tumor cells in the additionally resected area, indicating that the iMRI finding was a tumor mimic. Six months later, the T2 high-signal area around the resection cavity had disappeared on MRI without any additional treatment.This case highlights the challenge of distinguishing between T2 hyperintense mimicry and tumor enlargement during glioma surgery seen on iMRI. Despite the significant value of iMRI, our report underscores the need for careful interpretation in neurosurgical practice, particularly with non–contrast-enhancing tumors.