BRAF V600E mutation mediates FDG-methionine uptake mismatch in polymorphous low-grade neuroepithelial tumor of the young

Systematic review and cumulative analysis of clinical properties of BRAF V600E mutations in PLNTY histological samples

PURPOSE

Polymorphous low-grade neuroepithelial tumors of the young (PLNTY) represent a rare pediatric-type tumor that most commonly presents as medically refractory epilepsy. PLNTY has only recently been recognized as a distinct clinical entity, having been first described in 2016 and added to the World Health Organization classification of CNS tumors in 2021. Molecular studies have determined that PLNTY is uniformly driven by aberrant MAPK pathway activation, with most tumors carrying either a BRAF V600E mutation or activating FGFR2 or FGFR3 fusion protein. Although it is known that these driver mutations are mutually exclusive, little is known about differences in clinical presentation or treatment outcomes between PLNTY cases driven by these distinct mutations.

METHODS

We performed a systematic review and cumulative analysis of PLNTY cases to assess whether or not PLNTY tumors carrying the BRAF V600E mutation exhibit different clinical behaviors. By searching the literature for all cases of PLNTY wherein BRAF V600E status was characterized, we compiled a dataset of 62 unique patient instances. Using a logistic regression-based approach, we assessed a primary outcome of what factors of a clinical presentation were associated with BRAF V600E mutations and a secondary outcome of what factors predicted total seizure freedom post-surgical resection.

RESULTS

PLNTY cases carrying BRAF V600E mutations in the literature were strongly positively associated with adult patients (p = 0.0055, OR = 6.556; 95% Conf. Int. = 1.737-24.742). BRAF V600E status was also positively associated with tumor involvement of the temporal lobe (p = 0.0046, OR = 11.036; 95% Conf. Int. = 2.100-58.006). Male sex was also positively associated with BRAF V600E status, but the result did not quite achieve statistical significance (p = 0.0731). BRAF V600E status was not found to be associated with post-operative seizure freedom.

CONCLUSIONS

These findings indicate that BRAF V600E-positive PLNTY exhibit characteristic clinical presentations but are not necessarily different in treatment responsiveness. Non-BRAF V600E tumors are more commonly associated with young patients.

Polymorphous low-grade neuroepithelial tumour of young (PLNTY): the new kid on the block

INTRODUCTION

Polymorphous low grade neuroepithelial tumor of the young (PLNTY) is a newly described epileptogenic tumor first reported by Jason. T. Huse et al. in 2016. Only a very few cases have been reported so far and has been recently incorporated in the World Health Organization (WHO) Central Nervous System Classification of tumours, 5th edition, 2021. Here we report a rare case of PLNTY which closely resembles DNET (Dysembryoplastic neuroepithelial tumor) with plenty of interesting findings which would otherwise go unnoticed resulting in a nonspecific or misclassified diagnosis.

CASE REPORT

A 12 year old boy presented to the Neurosurgery OPD with seizures for the past five years and was given multiple antiepileptics for the same. Magnetic resonance imaging (MRI) showed a well-defined lobulated cortical mass with T1 hypo intensity and T2 hyperintensity in the left temporal lobe measuring 2.1 × 2 × 1.3 cm suggesting a DNET. Left temporal craniotomy and excision of the lesion was done. Frozen section showed features of a low grade glial neoplasm. Routine sections demonstrated polymorphous findings including oligodendroglia like features, neuronal nuclear pleomorphism, spindled astroglial elements, perivascular rosettes, calcification, and vascular mineralization. By immunohistochemistry (IHC), the tumor cells were diffusely positive for GFAP and CD34.Ki67 labelling index was low. A final diagnosis of PLNTY was made based on the above findings. The child has been epilepsy free since the past one-month post-surgery and is on follow up.

DISCUSSION/CONCLUSION

PLNTY is a newly discovered distinct pediatric low grade glial neoplasm which was earlier grouped into nonspecific forms of DNET. It is characterized morphologically and molecularly by the presence of oligodendroglial component, CD34 expression, BRAFV600E mutation and alterations in the MAP kinase pathway. They are known to behave in a low-grade fashion amenable to control by excision with occasional cases of recurrence reported. It is important to recognize and report similar tumors to determine the long-term risk of recurrence and create a more complete understanding on their radiology and molecular genetics.

[11C]-methionine positron emission tomography in the evaluation of pediatric low-grade gliomas

Background

[11C]-Methionine positron emission tomography (PET; [11C]-MET-PET) is principally used for the evaluation of brain tumors in adults. Although amino acid PET tracers are more commonly used in the evaluation of pediatric brain tumors, data on [11C]-MET-PET imaging of pediatric low-grade gliomas (pLGG) is scarce. This study aimed to investigate the roles of [11C]-MET-PET in the evaluation of pLGGs.

Methods

Eighteen patients with newly diagnosed pLGG and 26 previously treated pLGG patients underwent [11C]-MET-PET met the inclusion and exclusion criteria. Tumor-to-brain uptake ratio (TBR) and metabolic tumor volumes were assessed for diagnostic performances (newly diagnosed, 15; previously treated 26), change with therapy (newly diagnosed, 9; previously treated 7), and variability among different histology (n = 12) and molecular markers (n = 7) of pLGGs.

Results

The sensitivity of [11C]-MET-PET for diagnosing pLGG, newly diagnosed, and previously treated combined was 93% for both TBRmax and TBRpeak, 76% for TBRmean, and 95% for qualitative evaluation. TBRmax showed a statistically significant reduction after treatment, while other PET parameters showed a tendency to decrease. Median TBRmax, TBRpeak, and TBRmean values were slightly higher in the BRAFV600E mutated tumors compared to the BRAF fused tumors. Median TBRmax, and TBRpeak in diffuse astrocytomas were higher compared to pilocytic astrocytomas, but median TBRmean, was slightly higher in pilocytic astrocytomas. However, formal statistical analysis was not done due to the small sample size.

Conclusions

Our study shows that [11C]-MET-PET reliably characterizes new and previously treated pLGGs. Our study also shows that quantitative parameters tend to decrease with treatment, and differences may exist between various pLGG types.

Clinical significance of molecular subgroups of polymorphous low-grade neuroepithelial tumor of the young (PLNTY): A small single institutional case series and integrated analysis

INTRODUCTION

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently described entity. The clinicopathological features and prognosis of the molecular subgroups of these rare tumors is poorly understood. In this study, we presented a small case series of three new cases and integrated the data with published cases in the literature to characterize the similarities and differences of molecular subgroups of PLNTY.

METHODS

We searched our institutional archive for PLNTY cases and searched PubMed and Web of Science for relevant data. Demographic, clinical, radiologic, histopathological, molecular, and follow-up data of our four cases with published cases were integrated for final analyses.

RESULTS

We identified three institutional cases of PLNTY. The median age of our patients was 17 years (range: 13-42). All patients had a prior history of chronic seizures and all had tumors affecting the temporal lobes. Histopathologically, all cases showed oligodendroglial-like morphology with intratumoral calcifications and at least partially infiltrative growth patterns. Tumor cells were immunoreactive with CD34 and GFAP. Genetically, all cases harbored BRAF V600E mutations. Integrated analyses, including a total of 67 cases, demonstrated that PLNTYs with FGFR2 mutation were significantly younger (median age 11.0 years) than those with BRAF V600E or FGFR3 fusions (median age 41.0 and 16.0 years, respectively). All BRAF V600E-positive PLNTYs were free of tumor recurrence, while four of PLNTYs in other molecular subgroups developed tumor recurrence by imaging.

CONCLUSION

Our study suggests that PLNTYs have distinct clinicopathological features and are driven by genetic alterations in the MAPK pathway. The molecular subgroups of PLNTYs share similar findings, but also demonstrate distinct patient demographics.

Review on neuroimaging in pediatric-type diffuse low-grade gliomas

The fifth edition of the World Health Organization Classification of Tumors of the Central Nervous System (WHO CNS5) has identified a new classification system for tumors of the brain and spinal cord, highlighting the pivotal role of molecular diagnosis in accurately categorizing neoplasms. In addition to previous classifications, one of the key distinctions lies in categorizing pediatric-type diffuse low-grade gliomas (pDLGGs) and pediatric-type diffuse high-grade gliomas (pDHGGs) as distinct tumor types. Although similar in histology and morphology, pediatric diffuse gliomas are completely different from the adult type with respect to the molecular genetic characteristics, prognosis, and treatment strategies. pDLGG includes four tumor types, namely, diffuse astrocytoma, MYB- or MYBL1-altered; angiocentric glioma; polymorphous low-grade neuroepithelial tumor of the young (PLNTY); and diffuse low-grade glioma, MAPK pathway-altered, three types of which are newly recognized tumor types. Herein, we review the clinical characteristics, histopathological and molecular genetic characteristics, neuroimaging features, and prognosis of pDLGG and summarize the neuroimaging key points in diagnosing different tumor types. This review aims to evaluate and update the relevant pDLGG features and advances in neuroimaging that may assist in differential diagnosis, surgery planning, and prognostic determination of these tumor types and provide accurate diagnostic information for clinical colleagues.

Pediatric and elderly polymorphous low-grade neuroepithelial tumor of the young: Typical and unusual case reports and literature review

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY), one of the pediatric-type diffuse low-grade gliomas, is characterized by a diffuse infiltrating pattern of oligodendroglioma-like tumor cells showing CD34 positivity and harbors mitogen-activated protein kinase (MAPK) alteration, such as vRAF murine sarcoma viral oncogene homolog B1 (BRAF) p.V600E or fibroblast growth factor fusion genetically. It occurs mainly in pediatric and adolescents with seizures due to the dominant location of the temporal lobe. However, there have been a few cases of PLNTY in adult patients, suggesting the wide range of this tumor spectrum. Here, we describe two cases of PLNTY, one in a 14-year-old female and the other in a 66-year-old female. The pediatric tumor showed typical clinical course and histopathology with BRAF p.V600E mutation, whereas the elderly tumor was unusual because of non-epileptic onset clinically and ependymal differentiation histopathologically harboring KIAA1549-BRAF fusion. There might be unusual but possible PLNTY, as in our elderly case. We also compared typical pediatric and unusual elderly tumors by reviewing the literature.

Atypical presentation of polymorphous low-grade neuroepithelial tumor of young (PLNTY): a case report

The polymorphous low-grade neuroepithelial tumor of young (PLNTY) is considered as one among the low-grade neuroepithelial tumor; as per WHO-2021 classification of Brain Tumors in the fifth edition. The term PLNTY was first coined by Huse in 2016. These morphologically variable tumors are characterized by their oligodendroglioma-like cellular components, infiltrative growth pattern, and Cluster of Differentiation 34 (CD34) immunopositivity. Frequent genetic abnormalities involving mitogen-activated protein kinase pathway constituents like the BRAF proto-oncogene or fibroblast growth receptor 2/3 are harbored by PLNTYs. Radiologically, these are found to be well-circumscribed lesions with calcified and cystic components, affecting primarily temporal lobes. Clinically, they present with seizures/epilepsy in young adults (< 30 years). In the present manuscript we are reporting a case of 37-year-old male, presenting with a gradually progressive headache for 6 months, found to have a left frontal multiloculated cystic lesion with dystrophic calcifications. Based on the distinctive histopathological feature of the oligodendroglioma-like infiltrative lesion showing CD34 immunopositivity, a diagnosis of a polymorphous low-grade neuroepithelial tumor of young was made.

The landscape of common genetic drivers and DNA methylation in low-grade (epilepsy-associated) neuroepithelial tumors: A review

Low-grade neuroepithelial tumors (LNETs) represent an important group of central nervous system neoplasms, some of which may be associated to epilepsy. The concept of long-term epilepsy-associated tumors (LEATs) includes a heterogenous group of low-grade, cortically based tumors, associated to drug-resistant epilepsy, often requiring surgical treatment. LEATs entities can sometimes be poorly discriminated by histological features, precluding a confident classification in the absence of additional diagnostic tools. This study aimed to provide an updated review on the genomic findings and DNA methylation profiling advances in LNETs, including histological entities of LEATs. A comprehensive search strategy was conducted on PubMed, Embase, and Web of Science Core Collection. High-quality peer-reviewed original manuscripts and review articles with full-text in English, published between 2003 and 2022, were included. Results were screened based on titles and abstracts to determine suitability for inclusion, and when addressed the topic of the review was screened by full-text reading. Data extraction was performed through a qualitative content analysis approach. Most LNETs appear to be driven mainly by a single genomic abnormality and respective affected signaling pathway, including BRAF p.V600E mutations in ganglioglioma, FGFR1 abnormalities in dysembryoplastic neuroepithelial tumor, MYB alterations in angiocentric glioma, BRAF fusions in pilocytic astrocytoma, PRKCA fusions in papillary glioneuronal tumor, between others. However, these molecular alterations are not exclusive, with some overlap amongst different tumor histologies. Also, clustering analysis of DNA methylation profiles allowed the identification of biologically similar molecular groups that sometimes transcend conventional histopathological classification. The exciting developments on the molecular basis of these tumors reinforce the importance of an integrative histopathological and (epi)genetic classification, which can be translated into precision medicine approaches.

Paediatric-type diffuse low-grade gliomas: a clinically and biologically distinct group of tumours with a favourable outcome

The WHO 2021 classification of central nervous system cancers distinguishes diffuse gliomas that arise in adults (referred to as the "adult type") and those that arise in children (defined as "paediatric") based on clinical and molecular characteristics."). However, paediatric-type gliomas may occasionally be present in younger adults and occasionally adult-type gliomas may occur in children. Diffuse low-grade paediatric glioma includes diffuse astrocytoma altered by MYB or MYBL1, low-grade polymorphic juvenile neuroepithelial tumour, angiocentric glioma, and diffuse low-grade glioma with an altered MAPK pathway. Here, we examine these newly recognised entities according to WHO diagnostic criteria and propose an integrated diagnostic approach that can be used to separate these clinically and biologically distinct tumor groups.

Polymorphous low-grade neuroepithelial tumor of the young: Rare tumor and review of the literature

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently described low-grade neuroepithelial tumor with an infiltrative growth pattern and oligodendrocyte-like cells that are CD34 immunopositive. Correlating histology and results from molecular testing is critical to correctly diagnosing PLNTY, as its histologic appearance is similar to oligodendrogliomas and shares genetic abnormalities common to other low-grade epilepsy associated tumors (LEATs). In this case report, we describe a 31-year-old female with intractable epilepsy found to have a temporal mass and diagnosed with PLNTY after histopathologic and molecular testing. We describe the radiographic, histologic, and genetic features in relation to the epileptic and oncologic outcomes for this patient. Then, we compare these features and outcomes to other cases of PLNTY described in the literature.

Clinical, Radiological, Pathological Features and Seizure Outcome With Surgical Management of Polymorphous Low-Grade Neuroepithelial Tumor of the Young Associated With Epilepsy

Objective

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a novel distinct epileptogenic neoplasm, and its clinical, imaging, histopathological, and molecular features were already known in the existing literature. We aimed to analyze the surgical management of PLNTY combined with these known characteristics.

Methods

Eight patients underwent surgical treatment in our center between December 2017 and December 2020, and the postoperative pathology was diagnosed as PLNTY. Their clinical data, imaging, pathological, molecular characteristics, and seizure outcome were retrospectively analyzed. Follow-up evaluations and a literature review were performed.

Results

The 8 patients included 1 woman and 7 men, aged between 5 and 51 years old (mean = 31.6, median = 29). The preoperative symptoms of all 8 cases were seizures. Four tumors were situated in the temporal lobes, and one of the four extratemporal tumors was in the occipital lobe and three were in the frontal lobe. Enlarged and gross total resections were performed in 2 cases and the other 6 cases, respectively. All cases exhibited intense labeling of CD34, and absence of 1p/19q codeletion and IDH1 or IDH2 mutation. B-Raf proto-oncogene (BRAF) V600E mutation was presented in 4 (66.7%) of 6 detected cases. The postoperative seizure outcome of Engel class I was achieved in 6 cases (75%).

Conclusion

PLNTY represents distinctive histologic, immunophenotypic and biomolecular features, and has high epileptogenicity. Early surgical intervention and enlarged resection of PLNTY associated with epilepsy will help to improve the postoperative seizure-free rate.

Neuroradiological features of the polymorphous low-grade neuroepithelial tumor of the young: five new cases with a systematic review of the literature

PURPOSE

Polymorphous low-grade neuroepithelial tumors of the young (PLNTY) is a newly recognized brain tumor with genetic abnormalities frequently involving either BRAF or FGFR2/FGFR3. There are few publications available about the neuroradiological features of PLNTY. In this systematic review, we assessed the demographic, clinical, and neuroradiological features of PLNTY.

METHODS

Literature data were extracted from database searches in MEDLINE and SCOPUS databases up to June 10, 2021. Studies reporting on pathologically proven PLNTY with neuroradiological findings were included. After reviewing 103 abstracts, 9 articles encompassing 19 cases met the inclusion criteria. We also added five patients from our hospital. The correlations between the presence of "transmantle-like sign" and the following three factors: duration of seizures; tumor size; and pathologically proven cortical dysplasia, were examined.

RESULTS

The median patient age was 15.5 years (range, 5-57 years), and 15/24 (62.5%) were female. All tumors were localized supratentorialy. The main radiological features included cortical or subcortical masses (95.8%) in the temporal lobe (66.7%), calcification (83.3%), well-defined margins (72.7%), solid and cystic components (66.6%), and T2-weighted imaging (T2WI) hyperintensity (50.0%). The duration of seizure was significantly longer (positive vs. negative (median [range]), 24 months [6 - 96 months] vs. 5 months [1 - 12 months], p = 0.042), and the presence of the cortical dysplasia was significantly more frequent (3/8 vs 0/16, p = 0.042) in the patients with transmantle-like sign.

CONCLUSION

PLNTY typically represents a calcified, well-defined mass in the supratentorial cortical or subcortical regions. The radiological findings defined here could facilitate the diagnosis of PLNTY.

A "polymorphous low-grade neuroepithelial tumor of the young (PLNTY)" diagnosed in an adult. Report of a case and review of the literature

Background:

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a rare neuropathological entity, recently introduced in neuro-oncology. These tumors, histologically similar to oligodendrogliomas, cause epilepsy, occurring in children and young adults. Only few cases of PLNTY have been described in literature and all reported cases invariably focused on the onset of these tumors in children and young adults.

Case Description:

We report the case of a 50-year-old woman suffering from epilepsy since the 1^st year of her life. Computed tomography scan and magnetic resonance imaging of the brain documented the presence of a calcified mass involving left temporal lobe. The tumor was surgically excised and the histological examination showed a hypocellular and massively calcified neoplasm with morphological and immunohistochemical features consistent with the diagnosis of “PLNTY.”

Conclusion:

A review of the literature revealed that there are 31 cases of PLNTY reported in literature, most of which are children or young adults. The present case represents the second PLNTY diagnosed in a middle-aged adult to the best of our knowledge, suggesting that PLNTY should always be included in the differential diagnosis of low-grade brain tumors, also in adult patients.