Molecular features of pleomorphic xanthoastrocytoma

Comparing loss of p16 and MTAP expression in detecting CDKN2A homozygous deletion in pleomorphic xanthoastrocytoma

Pleomorphic xanthoastrocytomas (PXAs) harbor CDKN2A homozygous deletion in >90% of cases, resulting in loss of p16 expression by immunohistochemistry. Considering the proximity of MTAP to CDKN2A and their frequent concurrent deletions, loss of MTAP expression may be a surrogate for CDKN2A homozygous deletion. We evaluated p16 and MTAP expression in 38 patient PXAs (CNS WHO grade 2: n = 23, 60.5%; grade 3: n = 15, 39.5%) with available chromosomal microarray data to determine whether MTAP can be utilized independently or in combination with p16 to predict CDKN2A status. CDKN2A, CDKN2B, and MTAP homozygous deletion were present in 37 (97.4%), 36 (94.7%), and 25 (65.8%) cases, respectively. Expression of p16 was lost in 35 (92.1%) cases, equivocal in one (2.6%), and failed in 2 (5.3%), while MTAP expression was lost in 27 (71.1%) cases, retained in 10 (26.3%), and equivocal in one (2.6%). This yielded a sensitivity of 94.6% for p16 and 73.0% for MTAP in detecting CDKN2A homozygous deletion through immunohistochemistry. MTAP expression was lost in the 2 cases with failed p16 staining (combined sensitivity of 100%). Our findings demonstrate that combined p16 and MTAP immunostains correctly detect CDKN2A homozygous deletion in PXA, while MTAP expression alone shows reduced sensitivity.

Clinical, Morphological, and Molecular Study on Grade 2 and 3 Pleomorphic Xanthoastrocytoma

PURPOSE

Pleomorphic xanthoastrocytoma (PXA) is an uncommon astrocytoma that tends to occur in children and young adults and has a relatively favorable prognosis. The 2021 WHO classification of tumors of the central nervous system (CNS WHO), 5th edition, rates PXAs as grade 2 and grade 3. The histological grading was based on mitotic activity (≥2.5 mitoses/mm2). This study specifically evaluates the clinical, morphological, and, especially, the molecular characteristics of grade 2 and 3 PXAs.

METHODS

Between 2003 and 2021, we characterized 53 tumors with histologically defined grade 2 PXA (n = 36, 68%) and grade 3 PXA (n = 17, 32%).

RESULTS

Compared with grade 2 PXA, grade 3 PXA has a deeper location and no superiority in the temporal lobe and is more likely to be accompanied by peritumoral edema. In histomorphology, epithelioid cells and necrosis were more likely to occur in grade 3 PXA. Molecular analysis found that the TERT promoter mutation was more prevalent in grade 3 PXA than in grade 2 PXA (35% vs. 3%; p = 0.0005) and all mutation sites were C228T. The cases without BRAF V600E mutation or with necrosis in grade 3 PXA had a poor prognosis (p = 0.01).

CONCLUSION

These data define PXA as a heterogeneous astrocytoma. Grade 2 and grade 3 PXAs have different clinical and histological characteristics as well as distinct molecular profiles. TERT promoter mutations may be a significant genetic event associated with anaplastic progression. Necrosis and BRAF V600E mutation play an important role in the prognosis of grade 3 PXA.

Correlation of MTAP immunohistochemical deficiency with CDKN2A homozygous deletion and clinicopathological features in pleomorphic xanthoastrocytoma

Pleomorphic xanthoastrocytoma (PXA) is a rare tumor ranging from World Health Organization (WHO) grades 2-3 and can potentially recur and metastasize throughout the central nervous system (CNS). Cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) deletion is a frequent genomic alteration of PXA. Methylthioadenosine phosphorylase (MTAP) immunohistochemistry is a promising surrogate marker for CDKN2A homozygous deletion in different cancers but has not been examined in PXA. Therefore, we performed CDKN2A fluorescence in situ hybridization and MTAP immunohistochemistry on specimens from 23 patients with CNS WHO grades 2 (n = 10) and 3 (n = 13) PXAs, including specimens from primary and recurrent tumors, and determined whether MTAP immunohistochemistry correlated with CDKN2A homozygous deletion and clinicopathological features. CDKN2A homozygous deletion was detected in 30% (3/10) and 76.9% (10/13) of CNS WHO grades 2 and 3 PXAs, respectively. In addition, MTAP loss was inconsistent with CDKN2A homozygous deletion (sensitivity = 86.7%, specificity = 100%). Furthermore, CDKN2A homozygous deletion was correlated with WHO grade (p = 0.026) and the Ki-67 labeling index (p = 0.037). Therefore, MTAP immunostaining can be a suitable surrogate marker for CDKN2A homozygous deletions in PXAs, and CDKN2A homozygous deletions may be an important prognostic factor for PXAs.

Prognostic Factors of Low-Grade Gliomas in Adults

Adult low-grade gliomas are a rare and aggressive pathology of the central nervous system. Some of their characteristics contribute to the patient's life expectancy and to their management. This study aimed to characterize and identify the main prognostic factors of low-grade gliomas. The six-year retrospective study statistically analyzed the demographic, imaging, and morphogenetic characteristics of the patient group through appropriate parameters. Immunohistochemical tests were performed: IDH1, Ki-67, p53, and Nestin, as well as FISH tests on the CDKN2A gene and 1p/19q codeletion. The pathology was prevalent in females, with patients having an average age of 56.31 years. The average tumor volume was 41.61 cm³, producing a midline shift with an average of 7.5 mm. Its displacement had a negative impact on survival. The presence of a residual tumor resulted in decreased survival and is an independent risk factor for mortality. Positivity for p53 identified a low survival rate. CDKN2A mutations were an independent risk factor for mortality. We identified that a negative prognosis is influenced by the association of epilepsy with headache, tumor volume, and immunoreactivity to IDH1 and p53. Independent factors associated with mortality were midline shift, presence of tumor residue, and CDKN2A gene deletions and amplifications.

Lateral ventricle pleomorphic xanthoastrocytoma concurrent with Dandy-Walker complex: A case report

INTRODUCTION

Dandy-Walker complex and pleomorphic xanthoastrocytomas are both rare disease entities that typically manifest early in life and are associated with congenital etiological factors. Dandy-Walker complex is a cerebellar malformation associated with a series of anatomical changes. The disease onset is usually at birth or during infancy. Late onset in adulthood is uncommon. Pleomorphic xanthoastrocytoma is a rare WHO grade II astrocytic tumor affecting mainly young adults. Concomitant occurrence of Dandy-Walker complex and pleomorphic xanthoastrocytoma has not been previously reported.

PATIENT CONCERNS AND DIAGNOSIS

A 30-year-old woman with a previous history of unconfirmed resected lateral ventricle meningioma presented with severe headache for 1 day. Imaging examination revealed a mass in the right lateral ventricle with heterogeneous signal patterns, changes in the posterior fossa corresponding to a Dandy-Walker variant, and mild hydrocephalus.

INTERVENTIONS AND OUTCOMES

Surgical complete resection of the mass was achieved. postoperative histopathological examination confirmed WHO grade II pleomorphic xanthoastrocytoma. Three years postsurgery, ventriculoperitoneal shunt was performed due to worsening of hydrocephalus. The patient has since remained symptom-free.

CONCLUSION

This is the first report of concomitant occurrence of Dandy-Walker complex and pleomorphic xanthoastrocytoma. The association of neurological congenital malformation with intracranial neoplasms may be multifactorial, with underlying role of genetic mutations or chromosome alterations.

The evolution of pleomorphic xanthoastrocytoma: from genesis to molecular alterations and mimics

Pleomorphic xanthoastrocytomas (PXAs) are rare tumors accounting for less than 1% of astrocytomas. They commonly occur in young patients and have relatively favorable prognosis. However, they are well known to have heterogenous morphology and biological behavior with the potential to recur and disseminate throughout the central nervous system, especially their anaplastic counterparts. Recent advances in the molecular characterization have discovered BRAFp.V600E mutations in conjunction with CDKN2A/B deletions and TERTp mutations to be the most frequent alterations in PXAs. These tumors can present a diagnostic challenge as they share overlapping histopathological, genomic as well as methylation profile with various other tumor types, particularly epithelioid glioblastomas (eGBs). This review provides the spectrum of evolution of PXAs from their genesis to recent molecular insights and attempts to review pathogenesis and relationship to other tumors that they mimic especially eGB. It is postulated based on evidence from literature that PXA and eGB are possibly related and not distinct entities, being two ends of a continuous spectrum of malignant progression (grade 2-grade 4) with anaplastic PXA (grade 3) lying in between. Future WHO classifications will have to possibly redefine these tumors using more confirmatory data from larger studies.

Infrequent RAS mutation is not associated with specific histological phenotype in gliomas

BACKGROUND

Mutations in driver genes such as IDH and BRAF have been identified in gliomas. Meanwhile, dysregulations in the p53, RB1, and MAPK and/or PI3K pathways are involved in the molecular pathogenesis of glioblastoma. RAS family genes activate MAPK through activation of RAF and PI3K to promote cell proliferation. RAS mutations are a well-known driver of mutation in many types of cancers, but knowledge of their significance for glioma is insufficient. The purpose of this study was to reveal the frequency and the clinical phenotype of RAS mutant in gliomas.

METHODS

This study analysed RAS mutations and their clinical significance in 242 gliomas that were stored as unfixed or cryopreserved specimens removed at Kyoto University and Osaka National Hospital between May 2006 and October 2017. The hot spots mutation of IDH1/2, H3F3A, HIST1H3B, and TERT promoter and exon 2 and exon 3 of KRAS, HRAS, and NRAS were analysed with Sanger sequencing method, and 1p/19q codeletion was analysed with multiplex ligation-dependent probe amplification. DNA methylation array was performed in some RAS mutant tumours to improve accuracy of diagnosis.

RESULTS

RAS mutations were identified in four gliomas with three KRAS mutations and one NRAS mutation in one anaplastic oligodendroglioma, two anaplastic astrocytomas (IDH wild-type in each), and one ganglioglioma. RAS-mutant gliomas were identified with various types of glioma histology.

CONCLUSION

RAS mutation appears infrequent, and it is not associated with any specific histological phenotype of glioma.

Sequencing of a central nervous system tumor demonstrates cancer transmission in an organ transplant

This study uses DNA sequencing to trace a donor organ transplant–mediated cancer transmission and illustrates how precise molecular pathology profiles might reduce future risk for transplant recipients.

Four organ transplant recipients from an organ donor diagnosed with anaplastic pleomorphic xanthoastrocytoma developed fatal malignancies for which the origin could not be confirmed by standard methods. We identified the somatic mutational profiles of the neoplasms using next-generation sequencing technologies and tracked the relationship between the different samples. The data were consistent with the presence of an aggressive clonal entity in the donor and the subsequent proliferation of descendent tumors in each recipient. Deleterious mutations in BRAF, PIK3CA, SDHC, DDR2, and FANCD2, and a chromosomal deletion spanning the CDKN2A/B genes, were shared between the recipients’ lesions. In addition to demonstrating that DNA sequencing tracked a donor/recipient cancer transmission, this study established that the genetic profile of a donor tumor and its potential aggressive phenotype could have been determined before transplantation was considered. As the genetic correlates of tumor invasion and metastases become better known, adding genetic profiling by DNA sequencing to the data considered for transplant safety should be considered.

[Histomolecular diagnosis of glial and glioneuronal tumours]

While rare compared to extra-cranial neoplasms, glial and glioneuronal tumors are responsible of high morbidity and mortality. In 2016, the World Health Organization introduced histo-molecular ("integrated") diagnostics for central nervous system tumors based on morphology, immunohistochemistry and the presence of key genetic alterations. This combined phenotypic-genotypic classification allows for a more objective diagnostic of brain tumors. The implementation of such a classification in daily practice requires immunohistochemical surrogates to detect common genetic alterations and sometimes expensive and not widely available molecular biology techniques. The first step in brain tumor diagnostics is to inquire about the clinical picture and the imaging findings. When dealing with a glial tumor, the pathologist needs to assess its nature, infiltrative or circumscribed. If the tumor is infiltrative, IDH1/2 genes (prognostic marker) and chromosomes 1p/19q (diagnosis of oligodendroglioma) need to be assessed. If the tumor appears circumscribed, the pathologist should look for a neuronal component associated with the glial component (glioneuronal tumor). A limited immunohistochemistry panel will help distinguish between diffuse glioma (IDH1-R132H, ATRX, p53) and circumscribed glial/glioneuronal tumor (CD34, neuronal markers, BRAF-V600E), and some antibodies may reliably detect genetic alterations (IDH1-R132H, BRAF-V600E and H3-K27M mutations). Chromosomal imbalances (1p/19q codeletion in oligodendroglioma; chromosome 7 gain/chromosome 10 loss and EGFR amplification in glioblastoma) and gene rearrangements (BRAF fusion, FGFR1 fusion) will be identified by molecular biology techniques. The up-coming edition of the WHO classification of the central nervous system tumors will rely more heavily on molecular alterations to accurately diagnose and treat brain tumors.

Exploring DNA Methylation for Prognosis and Analyzing the Tumor Microenvironment in Pleomorphic Xanthoastrocytoma

Pleomorphic xanthoastrocytoma (PXA) is a rare type of brain tumor that affects children and young adults. Molecular prognostic markers of PXAs remain poorly established. Similar to gangliogliomas, PXAs show prominent immune cell infiltrate, but its composition also remains unknown. In this study, we correlated DNA methylation and BRAF status with clinical outcome and explored the tumor microenvironment. We performed DNA methylation in 21 tumor samples from 18 subjects with a histological diagnosis of PXA. MethylCIBERSORT was used to deconvolute the PXA microenvironment by analyzing the associated immune cell-types. Median age at diagnosis was 16 years (range 7-32). At median follow-up of 30 months, 3-year and 5-year overall survival was 73% and 71%, respectively. Overall survival ranged from 1 to 139 months. Eleven out of 18 subjects (61%) showed disease progression. Progression-free survival ranged from 1 to 89 months. Trisomy 7 and CDKN2A/B (p16) homozygous deletion did not show any association with overall survival (p = 0.67 and p = 0.74, respectively). Decreased overall survival was observed for subjects with tumors lacking the BRAF V600E mutation (p = 0.02). PXAs had significantly increased CD8 T-cell epigenetic signatures compared with previously profiled gangliogliomas (p = 0.0019). The characterization of immune cell-types in PXAs may have implications for future development of immunotherapy.

Predictors of outcome in pleomorphic xanthoastrocytoma

Background

Pleomorphic xanthoastrocytomas (PXA) are circumscribed gliomas that typically have a favorable prognosis. Limited studies have revealed factors affecting survival outcomes in PXA. Here, we analyzed the largest PXA dataset in the literature and identify factors associated with outcomes.

Methods

Using the Surveillance, Epidemiology, and End Results (SEER) 18 Registries database, we identified histologically confirmed PXA patients between 1994 and 2016. Overall survival (OS) was analyzed using Kaplan-Meier survival and multivariable Cox proportional hazard models.

Results

In total, 470 patients were diagnosed with PXA (males = 53%; median age = 23 years [14-39 years]), the majority were Caucasian (n = 367; 78%). The estimated mean OS was 193 months [95% CI: 179-206]. Multivariate analysis revealed that greater age at diagnosis (≥39 years) (3.78 [2.16-6.59], P < .0001), larger tumor size (≥30 mm) (1.97 [1.05-3.71], P = .034), and postoperative radiotherapy (RT) (2.20 [1.31-3.69], P = .003) were independent predictors of poor OS. Pediatric PXA patients had improved survival outcomes compared to their adult counterparts, in which chemotherapy (CT) was associated with worse OS. Meanwhile, in adults, females and patients with temporal lobe tumors had an improved survival; conversely, tumor size ≥30 mm and postoperative RT were associated with poor OS.

Conclusions

In PXA, older age and larger tumor size at diagnosis are risk factors for poor OS, while pediatric patients have remarkably improved survival. Postoperative RT and CT appear to be ineffective treatment strategies while achieving GTR confer an improved survival in male patients and remains the cornerstone of treatment. These findings can help optimize PXA treatment while minimizing side effects. However, further studies of PXAs with molecular characterization are needed.

Cerebellar pleomorphic xanthoastrocytoma in the setting of neurofibromatosis type-I: Does it portend a different prognosis? A case report and systematic review

BACKGROUND

Pleomorphic xanthoastrocytoma (PXA) is a rare brain tumor occurring supra- and infra-tentorially in both young adults and children. PXA is a benign tumor with a favorable prognosis. It is not traditionally considered as a neurofibromatosis type 1 (NF-1)-associated lesion, and its prognosis remains largely unknown, on the contrary to non-NF-1 PXA tumors.

OBJECTIVE

Herein, we present a rare case of cerebellar PXA in a patient with NF-1 and performed systematic review of NF-1-associated PXA.

METHOD

We present a case of NF-1-associated PXA arising in the cerebellar region. We also reviewed the literature in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines to identify published cases of cerebellar vs. non-cerebellar NF-1-associated PXA and NF1 vs. non-NF1 PXAs, highlighting their management paradigm, prognosis, and outcomes.

RESULT

Our systematic review yielded only four previously reported cases of NF-1-associated PXAs in the cerebellar region. Our review suggests that infratentorial PXAs have a higher recurrence and lower survival rates than non-cerebellar NF-1-associated PXAs and non-NF1 PXAs in general.

CONCLUSION

Early and precise diagnosis is important for these lesions with the aid of imaging features, histology, immunohistochemistry, and genetic markers. Surgical resection with goal of GTR remains the mainstay management strategy for PXA, with adjuvant therapy usually reserved for anaplastic or malignant lesions. The identification of BRAF-V600E mutation and role of BRAF inhibitors hold promise as a diagnostic tool and treatment modality, respectively, for PXAs, and their relationship to NF-1 is worth further exploration.

FOXI1 expression in chromophobe renal cell carcinoma and renal oncocytoma: a study of The Cancer Genome Atlas transcriptome-based outlier mining and immunohistochemistry

FOXI1 is a forkhead family transcription factor that plays a key role in differentiation and functional maintenance for the renal intercalated cell (IC). The diagnostic utility of FOXI1 is rarely studied thus far. Comparative analyses of FOXI1 mRNA expression in normal kidney tissue and different renal neoplasms including chromophobe renal cell carcinoma (chRCC), renal oncocytoma (RO), and other renal cell carcinomas were conducted using transcriptomic data from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus, and single-cell RNA-seq datasets, in combination with integrative analyses using mutant data, karyotype data, and digital slides for cases with anomalous FOXI1 expression in TCGA. Formalin-fixed, paraffin-embedded whole-tissue slides of varied primary renal neoplasms (n = 367) were subjected to FOXI1 staining for validating FOXI1 transcription levels. We confirmed that FOXI1 was significantly upregulated at mRNA levels in ICs, chRCCs, and ROs compared with other renal tubule cell and renal cell carcinoma subtypes. Furthermore, most of the cases with FOXI1 expression outliers were misclassified in the TCGA kidney cancer project. An underlying novel entity with frequent mutations involved in the mTOR pathway was also found. FOXI1 immunoreactivity was consistently noted in ICs of the distal nephron. FOXI1 staining was positive in 85 of 93 chRCCs and 13 of 18 ROs, respectively. FOXI1 staining was not seen in renal neoplasms (n = 254) derived from non-ICs. In conclusion, FOXI1 expression in normal kidney tissue is restricted to ICs. This cell type-specific expression is retained during neoplastic transformation from ICs to chRCCs or ROs. FOXI1 is thereby a potential biomarker of IC-related tumors.

Frequent KRAS mutations in oncocytic papillary renal neoplasm with inverted nuclei

AIMS

Papillary renal neoplasm with reverse polarity (PRNRP) is a newly documented rare tumour type. Its molecular pathological features have thus far been very little studied.

METHODS AND RESULTS

There were 13 PRNRP cases including 3 The Cancer Genome Atlas (TCGA) cases and our 10 cases in this study. The 3 TCGA cases were found by a combined analysis of GATA3 mRNA expression levels and digital slides from the TCGA papillary renal cell carcinoma project. KRAS codon 12 mutations were identified in the three PRNRPs from TCGA. Of our 10 PRNRP cases, the mutations were also discovered using Sanger sequencing in seven (77.8%) of nine cases with available DNA, where KRAS p.G12V (n = 3), p.G12D (n = 2), p.G12R (n = 1) and p.G12C (n = 1) alterations were found. PRNRP shared similar gene expression profiles with renal distal tubules via an interprofile correlation analysis. Gene set enrichment analysis revealed that genes involved in 'KEGG aldosterone regulated sodium reabsorption' or 'hallmark apical surface' were enriched in PRNRP. Moreover, polarised immunostaining patterns for L1CAM and EMA in the distal tubule were maintained in PRNRP.

CONCLUSIONS

These results imply that the tumour potentially originates from the distal tubule, especially from the cortical collecting duct, and probably retains its cell polarity, except for nuclear inversion. We therefore propose that oncocytic papillary renal neoplasm with inverted nuclei (OPRNIN) is a better name for this tumour type. OPRNIN is a kidney site-specific KRAS mutation neoplasm different from conventional papillary renal cell carcinoma.

Cerebellar Pleomorphic Xanthoastrocytoma with BRAF V600E Mutation

BACKGROUND

Pleomorphic xanthoastrocytoma (PXA) is a rare type of astrocytoma with a peak incidence from 10 to 19 years of age. PXA is found most commonly in the supratentorium. When it is present in atypical areas such as the infratentorium, it is often overlooked as a potential differential diagnosis.

CASE DESCRIPTION

This report discusses the case of an 18-year-old woman with a pure PXA in the left cerebellum. The case consists of interesting pathologic and molecular features which do not align with the literature about PXA: a positive finding for BRAF V600E mutation and a negative finding for cluster of differentiation 34 expression. A review of pure PXA cases in the infratentorium has also been completed.

CONCLUSIONS

To our knowledge, this is the first case of PXA in the infratentorium with BRAF V600E mutation. The case also highlights the clinical relevance of including PXA as a differential diagnosis for lesions of the infratentorium.

Anaplastic pleomorphic xanthoastrocytoma associated with an H3G34 mutation: a case report with review of literature

Here, we report a rare case of anaplastic pleomorphic xanthoastrocytoma (PXA) associated with an H3G34 mutation. A 12-year-old male presented with loss of appetite, vomiting, headache, and a generalized seizure, and CT revealed a 9.0 cm left frontal lobe mass with some septal walls and a localized high-density area suggestive of hemorrhage or calcification, causing severe midline shift. He emergently underwent subtotal resection and the tumor was morphologically diagnosed as anaplastic PXA. DNA sequencing identified an H3F3A G34R mutation and a TP53 R273H mutation, and immunohistochemically, ATRX nuclear expression was lost. In CNS tumors, H3G34 mutations are essentially detected in glioblastoma (GBM) or central nervous system primitive neuroectodermal tumors. Those tumors most likely comprise a single biological entity (high-grade glioma with H3G34 mutation) because of no significant difference in molecular profiling and prognosis between GBM and PNET morphologies. To our knowledge, our present case is the first one of anaplastic PXA associated with an H3G34 mutation, and whether it biologically corresponds to "high-grade glioma with H3G34 mutation" needs further studies.