Corrigendum: Pediatric CNS tumors and 2021 WHO classification: what do oncologists need from pathologists?

[This corrects the article DOI: 10.3389/fnmol.2024.1268038.].

Diffuse Gliomas with FGFR3::TACC3 Fusion: Morphological and Molecular Features and Classification Challenges.

FGFR3::TACC3 fusion is a driver, potentially targetable, genetic alteration identified in approximately 4% of high-grade diffuse gliomas and rare cases with low-grade histology. Herein, we review the genetic and epigenetic features of these tumors and highlight the challenges in their classification and grading. Diffuse gliomas with FGFR3::TACC3 fusion display unique histopathological and molecular features, including an oligodendroglioma-like appearance, calcifications, and CD34 extravascular immunoreactivity. High-grade tumors exhibit molecular alterations and a DNA methylation profile typical of glioblastoma, suggesting that they may represent a subtype clinically characterized by a slightly better prognosis. Tumors with low-grade morphology are genetically and epigenetically heterogeneous. Some, exclusive to adults, have molecular alterations typical of glioblastoma, although most do not match any methylation classes, using version 12.5 of the Heidelberg classifier. Another group, which mostly affects children or adolescents, lacks the molecular features of glioblastoma and has a DNA methylation profile similar to that of low-grade glioneuronal tumors. In conclusion, diffuse gliomas with FGFR3::TACC3 fusion do not constitute a distinct nosological entity, owing to their genetic and epigenetic diversity. Further studies are warranted to clarify the biological aggressiveness of tumors with low-grade histology to refine the grading and determine the optimal treatment strategy.

DKK3 Expression in Glioblastoma: Correlations with Biomolecular Markers.

Glioblastoma is the most common malignant primary tumor of the CNS. The prognosis is dismal, with a median survival of 15 months. Surgical treatment followed by adjuvant therapies such as radiotherapy and chemotherapy characterize the classical strategy. The WNT pathway plays a key role in cellular proliferation, differentiation, and invasion. The DKK3 protein, capable of acting as a tumor suppressor, also appears to be able to modulate the WNT pathway. We performed, in a series of 40 patients, immunohistochemical and Western blot evaluations of DKK3 to better understand how the expression of this protein can influence clinical behavior. We used a statistical analysis, with correlations between the expression of DKK3 and overall survival, age, sex, Ki-67, p53, and MGMT and IDH status. We also correlated our data with information included in the cBioPortal database. In our analyses, DKK3 expression, in both immunohistochemistry and Western blot analyses, was reduced or absent in many cases, showing downregulation. To date, no clinical study exists in the literature that reports a potential correlation between IDH and MGMT status and the WNT pathway through the expression of DKK3. Modulation of this pathway through the expression of DKK3 could represent a new tailored therapeutic strategy in the treatment of glioblastoma.

Pediatric CNS tumors and 2021 WHO classification: what do oncologists need from pathologists?

The fifth edition of the WHO Classification of Tumors of the Central Nervous System (CNS), published in 2021, established new approaches to both CNS tumor nomenclature and grading, emphasizing the importance of integrated diagnoses and layered reports. This edition increased the role of molecular diagnostics in CNS tumor classification while still relying on other established approaches such as histology and immunohistochemistry. Moreover, it introduced new tumor types and subtypes based on novel diagnostic technologies such as DNA methylome profiling. Over the past decade, molecular techniques identified numerous key genetic alterations in CSN tumors, with important implications regarding the understanding of pathogenesis but also for prognosis and the development and application of effective molecularly targeted therapies. This review summarizes the major changes in the 2021 fifth edition classification of pediatric CNS tumors, highlighting for each entity the molecular alterations and other information that are relevant for diagnostic, prognostic, or therapeutic purposes and that patients' and oncologists' need from a pathology report.

Decoding the puzzle: A multidisciplinary systematic review of adult brainstem glioma.

Adult brainstem gliomas (BSGs) are a group of rare central nervous system tumors with varying prognoses and controversial standard treatment strategies. To provide an overview of current trends, a systematic review using the PRISMA guidelines, Class of evidence (CE) and strength of recommendation (SR), was conducted. The review identified 27 studies. Surgery was found to have a positive impact on survival, particularly for focal lesions with CE II SR C. Stereotactic image-guided biopsy was recommended when resective surgery was not feasible with CE II and SR B. The role of systemic treatments remains unclear. Eight studies provided molecular biology data. This review gathers crucial literature on diagnosis and management of adult BSGs. It provides evidence-based guidance with updated recommendations for diagnosing and treating, taking into account recent molecular and genetic advancements. The importance of brain biopsy is emphasized to optimize treatment using emerging genetic-molecular findings and explore potential targeted therapies.

H3 K27M mutation in rosette-forming glioneuronal tumors: a potential diagnostic pitfall.

According to the fifth edition of the World Health Organization (WHO) classification of tumors of the central nervous system (CNS), diffuse midline glioma H3 K27-altered is a grade 4 infiltrative glioma that arises from midline anatomical structures and is characterized by the loss of H3 K27me3 and co-occurring H3 K27M mutation or EZHIP overexpression. However, the H3 K27M mutation has also been observed in circumscribed gliomas and glioneuronal tumors arising in midline anatomical structures, which may result in diagnostic pitfalls.Rosette-forming glioneuronal tumor (RGNT) is a CNS WHO grade 1 neoplasm that histologically features neurocytic and glial components and originates in midline anatomical structures.This study aimed to assess whether RGNTs, similar to other midline tumors, may exhibit immunohistochemical loss of H3 K27me3 and harbor the H3 K27M mutation.All seven analyzed RGNTs displayed immunohistochemical loss of H3 K27me3 in all tumor cells or H3 K27me3 mosaic immunostaining. In one case, H3 K27me3 loss was associated with the H3 K27M mutation, whereas the other six cases did not exhibit any H3 mutations or EZHIP overexpression. During a follow-up period of 23 months, the H3 K27M-mutant case remained unchanged in size despite partial resection, indicating that the H3 mutation may not confer higher biological aggressiveness to RGNT.The immunohistochemical loss of H3 K27me3 co-occurring with the H3 K27M mutation may result in the potential misdiagnosis of RGNT, especially in cases of small biopsy specimens consisting of only the glial component.

Tumor-associated microenvironment, PD-L1 expression and their relationship with immunotherapy in glioblastoma, IDH-wild type: A comprehensive review with emphasis on the implications for neuropathologists.

Although novel knowledge has been acquired on the molecular landscape of glioblastoma (GBM), a relatively few steps forward have been made regarding its therapy. With the increasing use of novel immunotherapeutic drugs capable of stimulating the antitumor inflammatory response, in the last decades numerous studies aimed to characterize the tumor-associated microenvironment (TME) and its relationship with the immunogenicity of GBM. In this regard, although the tumor-associated microglia and macrophages (TAMs) and PD-L1/PD-1 axis have been emerged as one of the most relevant components of the GBM TME and one of the potential molecular pathways targetable with immunotherapy, respectively. It has been supposed that TAMs may acquire different phenotypes, switching from M1 to M2 phenotypes, with tumor-suppressive and tumor-stimulating role depending on the different surrounding conditions. PD-L1 is a type 1 transmembrane protein ligand expressed by T-cells, B-cells and antigen-presenting cells, with a main inhibitory checkpoint role on tumor immune regulation. While PD-L1 immunohistochemical expression has been extensively investigated in many cancers, its usefulness in the evaluation of GBM response rates to immunotherapy and its standardized evaluation by immunohistochemistry are still debated. The present review paper focuses on the current "state of the art" about the relationship between TME, PD-L1/PD-1 pathway and immunotherapy in GBM, also providing neuropathologists with an updated guide about the clinical trials conducted with PD-L1 and PD-1 inhibitors.

CNS tumor with CREBBP::BCORL1 Fusion and pathogenic mutations in BCOR and CREBBP: expanding the spectrum of BCOR-altered tumors.

The fifth edition of the World Health Organization (WHO) classification of central nervous system (CNS) tumors introduced the new tumor type CNS tumor with BCOR internal tandem duplication (ITD), characterized by a distinct DNA methylation profile and peculiar histopathological features, including a circumscribed growth pattern, ependymoma-like perivascular pseudorosettes, microcystic pattern, absent or focal GFAP immunostaining, OLIG2 positivity, and BCOR immunoreactivity. We describe a rare case of a CNS tumor in a 45-year-old man with histopathological and immunohistochemical features overlapping the CNS tumor with BCOR internal tandem duplication (ITD) but lacking BCOR immunostaining and BCOR ITD. Instead, the tumor showed CREBBP::BCORL1 fusion and pathogenic mutations in BCOR and CREBBP, along with a DNA methylation profile matching the "CNS tumor with EP300:BCOR(L1) fusion" methylation class. Two CNS tumors with fusions between CREBBP, or its paralog EP300, and BCORL1, and approximately twenty CNS tumors with CREBBP/EP300::BCOR fusions have been reported to date. They exhibited similar ependymoma-like features or a microcystic pattern, along with focal or absent GFAP immunostaining, and shared the same DNA methylation profile. Given their morphological and epigenetic similarities, circumscribed CNS tumors with EP300/CREBBP::BCOR(L1) fusions and CNS tumors with BCOR ITD may represent variants of the same tumor type. The ependymoma-like aspect coupled with the lack of diffuse GFAP immunostaining and the presence of OLIG2 positivity are useful clues for recognizing these tumors in histopathological practice. The diagnosis should be confirmed after testing for BCOR(L1) gene fusions and BCOR ITD.

Atypical meningioma: Histopathological, genetic, and epigenetic features to predict recurrence risk.

Grading assessed according to World Health Organization (WHO) criteria is a major prognostic factor for determining the risk of recurrence in patients with meningiomas and establishing the most appropriate therapeutic strategy after surgery. However, the main issue is to predict the recurrence risk of WHO grade 2 meningioma and, more specifically, of the atypical subtype. Indeed, owing to a reported recurrence rate of 50%, either radiotherapy or observation is currently considered an option after gross total surgical resection of atypical meningiomas. These heterogeneous clinical outcomes are likely related to the broad histopathological diagnostic criteria for this subtype, and whether meningiomas only present as brain invasion should be classified as atypical remains controversial. Over the last few years, several studies have shown that DNA methylation profiling, next-generation sequencing, and transcriptomics can better stratify meningiomas for their recurrence risk than histology. The main limitations to the widespread use of these approaches to classify meningiomas are their high cost and the need for sophisticated technologies. However, all studies concurred that atypical meningiomas without chromosome 1p deletion display a low recurrence risk, suggesting that the assessment of this cytogenetic alteration could represent an easy and quick method to determine which patients could benefit from adjuvant treatment after surgery. In addition, prognostically unfavorable molecular groups can be distinguished using specific immunostainings, although further validation is required.

A diffuse glioma with oligodendroglial-like cells and extensive calcifications.

The tumor showed extensive microcalcifications and cells with oval, nuclei and a clear perinuclear halo (A), positive immunostaining for OLIG-2 (B), GFAP (C), and CD34 (D), and intermingled Neu-N-positive neurons (E). FISH revealed multiple signals for the centromere of chromosome 7 (gains) (green probe) and the EGFR locus (red probe) (F, left), and a single signal for the centromere of chromosome 10 (loss) (F, right).

Spinal ependymoma in adults: from molecular advances to new treatment perspectives.

Ependymomas are rare glial tumors with clinical and biological heterogeneity, categorized into supratentorial ependymoma, posterior fossa ependymoma, and spinal cord ependymoma, according to anatomical localization. Spinal ependymoma comprises four different types: spinal ependymoma, spinal ependymoma MYCN-amplified, myxopapillary ependymoma, and subependymoma. The clinical onset largely depends on the spinal location of the tumor. Both non-specific and specific sensory and/or motor symptoms can be present. Owing to diverse features and the low incidence of spinal ependymomas, most of the current clinical management is derived from small retrospective studies, particularly in adults. Treatment involves primarily surgical resection, aiming at maximal safe resection. The use of radiotherapy remains controversial and the optimal dose has not been established; it is usually considered after subtotal resection for WHO grade 2 ependymoma and for WHO grade 3 ependymoma regardless of the extent of resection. There are limited systemic treatments available, with limited durable results and modest improvement in progression-free survival. Thus, chemotherapy is usually reserved for recurrent cases where resection and/or radiation is not feasible. Recently, a combination of temozolomide and lapatinib has shown modest results with a median progression-free survival (PFS) of 7.8 months in recurrent spinal ependymomas. Other studies have explored the use of temozolomide, platinum compounds, etoposide, and bevacizumab, but standard treatment options have not yet been defined. New treatment options with targeted treatments and immunotherapy are being investigated. Neurological and supportive care are crucial, even in the early stages. Post-surgical rehabilitation can improve the consequences of surgery and maintain a good quality of life, especially in young patients with long life expectancy. Here, we focus on the diagnosis and treatment recommendations for adults with spinal ependymoma, and discuss recent molecular advances and new treatment perspectives.

Novel Advances in Treatment of Meningiomas: Prognostic and Therapeutic Implications.

Meningiomas are the most frequent histotypes of tumors of the central nervous system. Their incidence is approximately 35% of all primary brain tumors. Although they have the status of benign lesions, meningiomas are often associated with a decreased quality of life due to focal neurological deficits that may be related. The optimal treatment is total resection. Histological grading is the most important prognostic factor. Recently, molecular alterations have been identified that are specifically related to particular phenotypes and, probably, are also responsible for grading, site, and prognostic trend. Meningiomas recur in 10-25% of cases. In these cases, and in patients with atypical or anaplastic meningiomas, the methods of approach are relatively insufficient. To date, data on the molecular biology, genetics, and epigenetics of meningiomas are insufficient. To achieve an optimal treatment strategy, it is necessary to identify the mechanisms that regulate tumor formation and progression. Combination therapies affecting multiple molecular targets are currently opening up and have significant promise as adjuvant therapeutic options. We review the most recent literature to identify studies investigating recent therapeutic treatments recently used for meningiomas.

Meningioma Grading beyond Histopathology: Relevance of Epigenetic and Genetic Features to Predict Clinical Outcome.

Meningiomas are common tumors of the central nervous system. The grading system established by the World Health Organization (WHO) has recently included pTERT mutations and CDKN2A/B homozygous deletions as criteria for grade 3, owing to their association with increased recurrence risk. However, these alterations identify only a portion of meningiomas that are devoid of histopathological malignancy and are prone to recurrence. Over the last few years, the integration of epigenetic, genetic, transcriptomic, and proteomic profiling has led to the identification of three main groups of meningiomas with distinct clinical outcomes and peculiar genetic features. Meningiomas in the first group have the best prognosis, are distinguished by the lack of NF2 alterations and chromosomal instability, and may be responsive to cytotoxic drugs. Meningiomas in the second group have an intermediate prognosis and are characterized by NF2 alterations, mild chromosomal instability, and enrichment in immune cells. Meningiomas in the third group had the worst prognosis, displayed NF2 alterations coupled with high chromosomal instability, and were resistant to cytotoxic treatment. Classification into these three groups predicts the recurrence risk of meningiomas more accurately than WHO grading and could be applicable in routine practice, owing to the possibility of distinguishing the different groups by specific immunostaining.

Pre-diagnostic prognostic value of leukocytes count and neutrophil-to-lymphocyte ratio in patients who develop colorectal cancer.

Introduction: Emerging evidence is pointing towards a relevant role of immunity in cancer development. Alterations in leukocytes count and neutrophil-to-lymphocyte ratio (NLR) at diagnosis of colorectal cancer (CRC) seems to predict poor prognosis, but no data is available for the pre-diagnostic values. Methods: Retrospective analysis of patients who underwent surgery for CRC at our center (2005 - 2020). 334 patients with a complete blood count dating at least 24 months prior to diagnosis were included. Changes in pre-diagnosis values of leukocytes (Pre-Leu), lymphocytes (Pre-Lymph), neutrophils (Pre-Neut), and NLR (Pre-NLR) and their correlation with overall- (OS) and cancer-related survival (CRS) were analyzed. Results: Pre-Leu, Pre-Neut and Pre-NLR showed an increasing trend approaching the date of diagnosis, while Pre-Lymph tended to decrease. The parameters were tested for associations with survival after surgery through multivariable analysis. After adjusting for potential confounding factors, Pre-Leu, Pre-Neut, Pre-Lymph and Pre-NLR resulted independent prognostic factors for OS and CRS. On sub-group analysis considering the interval between blood sampling and surgery, higher Pre-Leu, Pre-Neut, and Pre-NLR and lower Pre-Lymph were associated with worse CRS, and the effect was more evident when blood samples were closer to surgery. Conclusion: To our knowledge, this is the first study showing a significant correlation between pre-diagnosis immune profile and prognosis in CRC.

Case report of a pediatric medulloblastoma with concurrent MYC and MYCN subclonal amplification in distinct populations of neoplastic cells.

Medulloblastomas (MDBs) are classified into molecular groups showing peculiar immunohistochemical and genetic features and distinct DNA methylation profile. Group 3 and group 4 MDBs have the worst prognosis; the former is treated with high-risk protocols and features MYC amplification, whereas the latter receives standard-risk protocols and harbors MYCN amplification. Herein, we report a unique case of MDB showing histological and immunohistochemical features consistent with non-SHH/non-WNT classic MDB, with both MYCN (30% of tumor cells) and MYC (5-10% tumor cells) amplification in distinct subclones of neoplastic cells at fluorescence in situ hybridization (FISH), characterized by specific patterns. In spite of MYC amplification in only a small percentage of tumor cells, this case had DNA methylation profile consistent with group 3, emphasizing the importance to test both MYC and MYCN amplifications at a single cell level using highly sensitive methods, such as FISH, for diagnostic and therapeutic purposes.

Atypical meningiomas with an immunohistochemical profile consistent with hypermetabolic or proliferative molecular groups show high mitotic index, chromosomal instability, and higher recurrence risk.

The use of adjuvant radiotherapy is controversial for atypical meningiomas undergoing gross total resection. It has recently been proposed that meningiomas may be classified into four molecular groups (MG): immunogenic (MG1), benign NF2-wildtype (MG2), hypermetabolic (MG3), and proliferative (MG4). The two latter have the worst prognosis, and it has been suggested that they can be identified using ACADL and MCM2 immunostainings. We studied 55 primary atypical meningiomas, treated with gross total resection and no adjuvant therapies, to assess whether ACADL and MCM2 immuno-expression may identify patients at higher recurrence risk, thus requiring adjuvant treatments. Twelve cases resulted ACADL-/MCM2-, 9 ACADL + /MCM2-, 17 ACADL + /MCM2 + , and 17 ACADL-/MCM2 + . MCM2 + meningiomas displayed more frequent atypical features (prominent nucleoli, small cells with high nuclear-to-cytoplasmic ratio) and CDKN2A hemizygous deletion (HeDe) (P = 0.011). The immunoexpression of ACADL and/or MCM2 was significantly associated with higher mitotic index, 1p and 18q deletions, increased recurrence rate (P = 0.0006), and shorter recurrence-free survival (RFS) (P = 0.032). At multivariate analysis, carried out including ACADL/MCM2 immuno-expression, mitotic index, and CDKN2A HeDe as covariates, this latter resulted a significant and independent prognosticator of shorter RFS (P = 0.0003).

Molecular Investigation of DKK3 in Cerebral Ischemic/Reperfusion Injury.

Dickkopf-3 (Dkk3) is an atypical member of the Dkk family of Wnt inhibitors, which has been implicated in the pathophysiology of neurodegenerative disorders. Its role in the mechanisms of cellular degeneration and protection is still unknown. The aim of our work is to investigate the endogenous activation of the DKK3 pathway in a model of transient occlusion of the middle cerebral artery in rats. In particular, the animals were subjected to 1 h of ischemia followed by different reperfusion times (1 h, 6 h, 12 h and 24 h) to evaluate the downstream pathway and the time course of its activation. Western blot analysis showed increased Dkk3 expression in animals with the highest time of reperfusion. The increased levels of Dkk3 were accompanied by reduced Wnt3a, Frz1 and PIWI1a expression in the cytosol while FOXM1 and ß-catenin decreased in the nucleus. These molecular changes led to an increase in the apoptotic pathway, as showed by the increased expression of Caspase 3 and Bax and the reduced levels of Bcl-2, and to a decrease in neurogenesis, as shown by the decreased expression of Tbr2, Ngn2 and Pax6. In the second part of the study, we decided to employ curcumin, an activator of the Wnt/ß-catenin signaling, to investigate its effect on Dkk3. In particular, curcumin was administered 1 and 6 h after ischemia, and animals were sacrificed 24 h later when the expression of Dkk3 was higher. Our data displayed that curcumin administration decreased Dkk3 expression, and increased Wnt3a, Frz1 and PIWI1a levels. Well in line with these data, curcumin administration increased nuclear ß-catenin and FOXM1 expression. The down-regulation of Dkk3 by curcumin led to reduced apoptosis and increased neurogenesis. Summarizing, our results showed that Dkk3 acts as an inhibitor of Wnt/ß-catenin signaling during cerebral ischemia. Additionally, its inhibition and the contextual activation of the Wnt/ß-catenin pathway are protective against ischemic stroke.

Histologic Definition of Enhancing Core and FLAIR Hyperintensity Region of Glioblastoma, IDH-Wild Type: A Clinico-Pathologic Study on a Single-Institution Series.

The extent of resection beyond the enhancing core (EC) in glioblastoma IDH-wild type (GBM, IDHwt) is one of the most debated topics in neuro-oncology. Indeed, it has been demonstrated that local disease recurrence often arises in peritumoral areas and that radiologically-defined FLAIR hyperintensity areas of GBM IDHwt are often visible beyond the conventional EC. Therefore, the need to extend the surgical resection also to the FLAIR hyperintensity areas is a matter of debate. Since little is known about the histological composition of FLAIR hyperintensity regions, in this study we aimed to provide a comprehensive description of the histological features of EC and FLAIR hyperintensity regions sampled intraoperatively using neuronavigation and 5-aminolevulinic acid (5-ALA) fluorescence, in 33 patients with GBM, IDHwt. Assessing a total 109 histological samples, we found that FLAIR areas consisted in: (i) fragments of white matter focally to diffusely infiltrated by tumor cells in 76% of cases; (ii) a mixture of white matter with reactive astrogliosis and grey matter with perineuronal satellitosis in 15% and (iii) tumor tissue in 9%. A deeper knowledge of the histology of FLAIR hyperintensity areas in GBM, IDH-wt may serve to better guide neurosurgeons on the choice of the most appropriate surgical approach in patients with this neoplasm.