Pathologic characteristics of pediatric intracranial pilocytic astrocytomas and their impact on outcome in 3 countries: a multi-institutional study

Clinical, histopathological and molecular risk factors for recurrence of pilocytic astrocytomas: brainstem/spinal location, nestin expression and gain of 7q and 19 are associated with early tumor recurrence

Pilocytic astrocytomas (PAs) are benign tumors. However, clinically aggressive PAs despite benign histology have been reported, and histological and molecular risk factors for prognosis have not been elucidated. 38 PAs were studied for clinical, histological, and molecular factors, including tumor location, extent of resection, post-operative treatment, glioma-associated molecules (IDH1/2, ATRX, BRAF, FGFR1, PIK3CA, H3F3A, p53, VEGF, Nestin, PD-1/PD-L1), CDKN2A/B deletion, and chromosomal number aberrations, to see if there is any correlation with patient's progression-free survival (PFS). Brainstem/spinal location, extent of resection and post-operative treatment, and VEGF-A, Nestin and PD-L1 expression, copy number gain of chromosome 7q or 19, TP53 mutation were significantly associated with shorter PFS. None of the histological parameters was associated with PFS. Multivariate analyses demonstrated that high Nestin expression, gain of 7q or 19, and extent of removal were independently predictive for early tumor recurrence. The brainstem/spinal PAs appeared distinct from those in the other sites in terms of molecular characteristics. Clinically aggressive PAs despite benign histology exhibited high Nestin expression. Brainstem/spinal location, extent of resection and some molecular factors including Nestin expression and gains of 7q and 19, rather than histological parameters, may be associated with early tumor recurrence in PAs.

Outcomes of Children With Low-Grade Gliomas in Low- and Middle-Income Countries: A Systematic Review

PURPOSE

Pediatric CNS tumors are increasingly a priority, particularly with the WHO designation of low-grade glioma (LGG) as one of six index childhood cancers. There are currently limited data on outcomes of pediatric patients with LGGs in low- and middle-income countries (LMICs).

METHODS

To better understand the outcomes of LGGs in LMICs, this systematic review interrogated nine literature databases.

RESULTS

The search identified 14,977 publications. Sixteen studies from 19 countries met the selection criteria and were included for data abstraction and analysis. Eleven studies (69%) were retrospective reviews from single institutions, and one (6%) captured institutional data prospectively. The studies captured a total of 957 patients with a median of 49 patients per study. Seven (44%) of the studies described the treatment modalities used. Of 373 patients for whom there was information, 173 (46%) had a gross total or near total resection, 109 (29%) had a subtotal resection, and 91 (24%) had only a biopsy performed. Seven studies, with a total of 476 patients, described the frequency of use of radiotherapy and/or chemotherapy in the cohorts: 83 of these patients received radiotherapy and 76 received chemotherapy. The 5-year overall survival ranged from 69.2% to 93.5%, although lower survival rates were reported at earlier time points. We identified limitations in the published studies with respect to the cohort sizes and methodologies.

CONCLUSION

The included studies reported survival rates frequently exceeding 80%, although the ultimate number of studies was limited, pointing to the paucity of studies describing the outcomes of children with LGGs in LMICs. This study underscores the need for more robust data on outcomes in pediatric LGG.

Diffuse GFAP Immunopositivity in the Oligodendrocyte-like Component of Pilocytic Astrocytoma Distinguishes It from Mimickers

Pilocytic astrocytoma with a predominant oligodendrocyte-like component can be difficult to distinguish from oligodendroglioma, dysembryoplastic neuroepithelial tumors (DNTs), central neurocytoma, and ependymoma (clear cell phenotype). The utility of GFAP immunostaining in this context is not well discussed. All cases with a diagnosis of pilocytic astrocytoma were retrieved from the pathological archives along with the following information: age, sex, and pathological description. The GFAP immunostaining was scored as score 1 (<25%), score 2 (25−50%), score 3 (50−75%), and score 4 (>75%). The comparison group included oligodendrogliomas, DNTs, ependymomas, and central neurocytomas. All 26 cases (16 males and 10 females) of pilocytic astrocytoma showed strong and diffuse (score 4) GFAP immunostaining in the neoplastic cells of both the solid fibrillary and oligodendrocyte-like components. The staining pattern in the neoplastic round cells in the oligodendrocyte-like areas was perinuclear cytoplasmic with no processes. In the comparison group, GFAP immunostaining was mostly restricted to the reactive astrocytes in the background. Focal areas of the neoplastic cells showed scores of 1−3 in the neoplastic cells, but the staining pattern was different from those in pilocytic astrocytoma. In the setting of tumors with predominant oligodendrocyte-like areas, the GFAP immunostaining score and pattern help distinguish pilocytic astrocytoma from its mimickers.

Molecular profiling and targeted therapy in pediatric gliomas: review and consensus recommendations

As the field of neuro-oncology makes headway in uncovering the key oncogenic drivers in pediatric glioma, the role of precision diagnostics and therapies continues to rapidly evolve with important implications for the standard of care for clinical management of these patients. Four studies at major academic centers were published in the last year outlining the clinically integrated molecular profiling and targeting of pediatric brain tumors; all 4 demonstrated the feasibility and utility of incorporating sequencing into the care of children with brain tumors, in particular for children and young adults with glioma. Based on synthesis of the data from these studies and others, we provide consensus recommendations for the integration of precision diagnostics and therapeutics into the practice of pediatric neuro-oncology. Our primary consensus recommendation is that next-generation sequencing should be routinely included in the workup of most pediatric gliomas.

Novel Surgical and Radiologic Risk Factors for Progression or Recurrence of Pediatric Pilocytic Astrocytoma

INTRODUCTION

Pilocytic astrocytomas (PA) are a common, benign childhood tumor known for their slow growth rates and excellent prognosis. The aim of our study was to characterize patient, tumor, and imaging-related risk factors for recurrence and progression of disease.

METHODS

We identified 116 patients with PA who underwent surgery at our institution between 2000 and 2015. Data were collected retrospectively from the clinical charts.

RESULTS

The mean age at resection was 7 ± 5 years (range 0.5-31) and mean follow-up was 6 ± 3 years. Initial resection was complete in 33 patients (29%), subtotal in 78 patients (67%), and biopsy in 5 patients (4%). A total of 45/116 (40%) patients experienced either recurrence or progression after initial resection with a mean time to recurrence or progression of 2.2 years. Bivariate analysis identified subtotal resection, tumor location, age at diagnosis, and imaging features (i.e., T2 invasion, exophytic component, hemorrhage, and solid tumors) as factors significantly associated with recurrence or progression (p < 0.05). Conversely, PAs that were completely resected, predominately cystic, and located in the cerebellum were significantly associated with no recurrence or progression (p < 0.05). Multivariate regression analysis narrowed down 4 robust risk factors: extent of resection, T2 invasion, predominantly solid lesions, and presence of an exophytic component (p < 0.05).

CONCLUSION

Total surgical removal of PA has been the most important prognostic factor for the clinical course of PA. Our study reveals additional risk factors for the recurrence or progression of disease: tumor invasion, solid composition, and tumors with an exophytic component.

Recent Progress in the Pathology and Genetics of Pilocytic and Pilomyxoid Astrocytomas

Pilocytic and pilomyxoid astrocytomas are some of the most common gliomas in children and young adults. These gliomas are indolent neoplasms with long overall survival probability. The genetic characteristics of these neoplasms are well known, and our deepened understanding of their associated molecular alterations has led to the development of novel treatment strategies and approaches. Currently, we can account for some of the unusual behavior, such as oncogene-induced senescence, associated spontaneous regression, anaplastic transformation, and cerebrospinal dissemination, of these gliomas. Nevertheless, enigmatic issues continue to surround these chronic tumors. Here, we review the classical and uncommon clinical pathological and genetic features of these indolent gliomas.

Genetic alterations related to BRAF-FGFR genes and dysregulated MAPK/ERK/mTOR signaling in adult pilocytic astrocytoma

Pilocytic astrocytomas occur rarely in adults and show aggressive tumor behavior. However, their underlying molecular-genetic events are largely uncharacterized. Hence, 59 adult pilocytic astrocytoma (APA) cases of classical histology were studied (MIB-1 LI: 1%-5%). Analysis of BRAF alterations using qRT-PCR, confirmed KIAA1549-BRAF fusion in 11 (19%) and BRAF-gain in 2 (3.4%) cases. BRAF-V600E mutation was noted in 1 (1.7%) case by sequencing. FGFR1-mutation and FGFR-TKD duplication were seen in 7/59 (11.9%) and 3/59 (5%) cases, respectively. Overall 36% of APAs harbored BRAF and/or FGFR genetic alterations. Notably, FGFR related genetic alterations were enriched in tumors of supratentorial region (8/25, 32%) as compared with other locations (P = 0.01). The difference in age of cases with FGFR1-mutation (Mean age ± SD: 37.2 ± 15 years) vs. KIAA1549-BRAF fusion (Mean age ± SD: 25.1 ± 4.1 years) was statistically significant (P = 0.03). Combined BRAF and FGFR alterations were identified in 3 (5%) cases. Notably, the cases with more than one genetic alteration were in higher age group (Mean age ± SD: 50 ± 12 years) as compared with cases with single genetic alteration (Mean age ± SD: 29 ± 10; P = 0.003). Immunopositivity of p-MAPK/p-MEK1 was found in all the cases examined. The pS6-immunoreactivity, a marker of mTOR activation was observed in 34/39 (87%) cases. Interestingly, cases with BRAF and/or FGFR related alteration showed significantly lower pS6-immunostatining (3/12; 25%) as compared with those with wild-type BRAF and/or FGFR (16/27; 59%) (P = 0.04). Further, analysis of seven IDH wild-type adult diffuse astrocytomas (DA) showed FGFR related genetic alterations in 43% cases. These and previous results suggest that APAs are genetically similar to IDH wild-type adult DAs. APAs harbor infrequent BRAF alterations but more frequent FGFR alterations as compared with pediatric cases. KIAA1549-BRAF fusion inversely correlates with increasing age whereas FGFR1-mutation associates with older age. Activation of MAPK/ERK/mTOR signaling appears to be an important oncogenic event in APAs and may be underlying event of aggressive tumor behavior. The findings provided a rationale for potential therapeutic advantage of targeting MAPK/ERK/mTOR pathway in APAs.

Current Understanding of BRAF Alterations in Diagnosis, Prognosis, and Therapeutic Targeting in Pediatric Low-Grade Gliomas

The mitogen-activated protein kinase (MAPK) pathway is known to play a key role in the initiation and maintenance of many tumors as well as normal development. This often occurs through mutation of the genes encoding RAS and RAF proteins which are involved in signal transduction in this pathway. BRAF is one of three RAF kinases which act as downstream effectors of growth factor signaling leading to cell cycle progression, proliferation, and survival. Initially reported as a point mutation (V600E) in the majority of metastatic melanomas, other alterations in the BRAF gene have now been reported in a variety of human cancers including papillary thyroid cancer, colon carcinomas, hairy cell leukemia, and more recently in gliomas. The identification of oncogenic mutations in the BRAF gene have led to a revolution in the treatment of metastatic melanoma using targeted molecular therapies that affect the MAPK pathway either directly through BRAF inhibition or downstream through inhibition of MEK. This review describes the molecular biology of BRAF in the context of pediatric low-grade gliomas, the role of BRAF as a diagnostic marker, the prognostic implications of BRAF, and evidence for therapeutic targeting of BRAF.

Therapeutic targets in pilocytic astrocytoma based on genetic analysis

Pilocytic astrocytoma (PA) is the most common astrocytic neoplasm of childhood. Patients have an extremely favorable prognosis after surgical resection, qualifying tumors for a grade I designation by the World Health Organization. The molecular data on PA support a key role for the BRAF oncogene in the pathogenesis of these tumors, with the KIAA1549-BRAF fusion being the most common alteration identified in sporadic cases, particularly those occurring in the posterior fossa. Constitutive activation of BRAF leads to downstream activation of the MEK/MAPK/ERK/p16 pathway, which interestingly is also used by cells to activate oncogene-induced senescence (OIS). In fact, the presence of an active OIS pathway might explain the periods of dormancy or spontaneous regression or both, that can be seen in PA. In addition to reviewing the historical evolution, clinicopathologic, predictive, prognostic, and molecular features of PA, we discuss current therapeutic strategies and the caveats that should be considered for the development of therapies that could be used to more effectively treat challenging cases. Individualized treatment requires identification of the type of MAPK alteration, as several alterations in BRAF have been described in addition to the KIAA1549-BRAF fusion. Combination regimens would also appear crucial to achieve tumor eradication and prevent the development of drug resistance. Balancing mitogen-activated protein kinases (MAPK) pathway inhibition with abrogation of an active OIS should be carefully considered as well to preserve any existing protective pathways. Importantly, PAs are largely indolent tumors, and care should be taken to avoid overtreatment, as aggressive therapy could cause more harm than good.

Practical molecular pathologic diagnosis of pilocytic astrocytomas

The pilocytic astrocytoma is predominantly a tumor of childhood and the most common type of circumscribed astrocytoma. The indolent nature of this tumor allows for prolonged survival for most patients, rendering the disease a rather "chronic" one, with potential long-term sequelae that are occasionally related to treatment. Two critical features of this tumor are its tendency to remain dormant, or involute even after subtotal resection, and the exceptional anaplastic transformation, sometimes following adjuvant therapy. The biological behavior of pilocytic astrocytoma can often be related to molecular alterations in the MAPK pathway.

The evolving molecular genetics of low-grade glioma

Low-grade gliomas (LGG) constitute grades I and II tumors of astrocytic and grade II tumors of oligodendroglial lineage. Although these tumors are typically slow growing, they may be associated with significant morbidity and mortality because of recurrence and malignant progression, even in the setting of optimal resection. LGG in pediatric and adult age groups are currently classified by morphologic criteria. Recent years have heralded a molecular revolution in understanding brain tumors, including LGG. Next-generation sequencing has definitively demonstrated that pediatric and adult LGG fundamentally differ in their underlying molecular characteristics, despite being histologically similar. Pediatric LGG show alterations in FGFR1 and BRAF in pilocytic astrocytomas and FGFR1 alterations in diffuse astrocytomas, each converging on the mitogen-activated protein kinase signaling pathway. Adult LGG are characterized by IDH1/2 mutations and ATRX mutations in astrocytic tumors and IDH1/2 mutations and 1p/19q codeletions in oligodendroglial tumors. TERT promoter mutations are also noted in LGG and are mainly associated with oligodendrogliomas. These findings have considerably refined approaches to classifying these tumors. Moreover, many of the molecular alterations identified in LGG directly impact on prognosis, tumor biology, and the development of novel therapies.

Glioma diagnostics and biomarkers: an ongoing challenge in the field of medicine and science

Glioma is the most common brain tumor. For the more aggressive form, glioblastoma, standard treatment includes surgical resection, irradiation with adjuvant temozolomide and, on recurrence, experimental chemotherapy. However, the survival of patients remains poor. There is a critical need for minimally invasive biomarkers for diagnosis and as measures of response to therapeutic interventions. Glioma shed extracellular vesicles (EVs), which invade the surrounding tissue and circulate within both the cerebrospinal fluid and the systemic circulation. These tumor-derived EVs and their content serve as an attractive source of biomarkers. In this review, we discuss the current state of the art of biomarkers for glioma with emphasis on their EV derivation.

Pilocytic astrocytomas of the optic nerve and their relation to pilocytic astrocytomas elsewhere in the central nervous system

Pilocytic astrocytoma is a low-grade glioma that affects mostly children and young adults and can occur anywhere in the central nervous system. Pilocytic astrocytoma of the optic nerve is an equally indolent subtype that is occasionally associated with neurofibromatosis type 1. In earlier studies, this subtype was considered within the larger category of 'optic pathway glioma,' which included infiltrating astrocytomas and other hypothalamic tumors. However, there have been suggestions that gliomas in the optic nerve, and especially pilocytic astrocytoma of the optic nerve, are biologically different from tumors within the hypothalamus and other parts of the optic tract. Furthermore, the recent discovery of BRAF duplication and fusion with the KIAA1549 gene is reported to be more typical for posterior fossa tumors, and the rate of this aberration is not well known in pilocytic astrocytoma of the optic nerve. To determine the distinction of pilocytic astrocytoma of the optic nerve from pilocytic astrocytoma of the posterior fossa and to investigate the prevalence of BRAF aberrations, we reviewed the clinicopathological and molecular features of all such patients in our institution. Our study demonstrates that BRAF duplication is more frequent in posterior fossa tumors compared with pilocytic astrocytoma of the optic nerve (P=0.011). However, the rates of phospho-MAPK1 and CDKN2A expression were high in both pilocytic astrocytoma of the optic nerve and posterior fossa pilocytic astrocytoma, suggesting that the MAPK pathway is active in these tumors. Our study supports the notion that BRAF duplication is more typical of posterior fossa pilocytic astrocytoma and that molecular alterations other than KIAA1549 fusion may underlie MAPK pathway activation in pilocytic astrocytoma of the optic nerve.

Insulin-like growth factor 2 mRNA binding protein 3 expression is an independent prognostic factor in pediatric pilocytic and pilomyxoid astrocytoma

Prognostic factors in pilocytic astrocytomas (PAs) and pilomyxoid astrocytomas (PMAs) include extent of resection, location, and age, but no molecular markers have been established. Insulin-like growth factor 2 mRNA binding protein 3 (IMP3, IGF2BP3) is predictive of an unfavorable prognosis in other tumors, including high-grade astrocytomas, but its role in PA/PMA is unknown. This study aimed to determine the expression and prognostic value of IMP3 in pediatric PA/PMAs. Insulin-like growth factor 2 mRNA binding protein 3 protein expression was examined by immunohistochemistry in 77 pediatric PAs (n = 70) and PMAs (n = 7) and scored on a subjective scale. Strong diffuse staining for IMP3 was observed in 31% (24 of 77) of tumors and associated with a shorter progression-free survival (hazard ratio, 2.63; p = 0.008). This cohort confirmed previously identified prognostic factors, including extent of resection, age, and tumor location. Currently, only clinical factors are weighed to stratify risk for patients and to identify those who should receive further therapy. Multivariate analyses identified IMP3 expression as an independent prognostic factor when combined with high-/low-risk stratification (hazard ratio, 2.45; p = 0.016). High IMP3, as assessed by immunohistochemistry, has potential use as an additional predictor of poor prognosis in pediatric PA/PMAs and warrants evaluation in larger cohorts.

The diagnostic role and clinical relevance of determination of BRAF status in brain tumors

BRAF protein is a serine/threonine kinase that serves as an immediate downstream effector of the MAPK signaling cascade, a signal transduction pathway that modulates cell proliferation and survival. BRAF alterations leading to MAPK pathway activation have been identified in gliomas and glioneuronal tumors of the CNS. Whereas BRAF mutations have been found in a wide spectrum of CNS tumors, BRAF fusions have been almost exclusively found in pilocytic astrocytomas. BRAF fusion identification provides an additional help in the differential diagnosis of supratentorial gliomas. Although the prognostic significance of BRAF alterations in different CNS tumors is still under investigation, the evidence of BRAF-dependent MAPK-pathway activation in gliomas has moreover drawn attention to the potential use of MEK1/2 and RAF inhibitors in clinical neuro-oncology. Given the promising results of the therapeutic management of several cancer types, clinical studies investigating the suitability of such inhibitors for the therapy of gliomas are ongoing.

Evidence for new targets and synergistic effect of metronomic celecoxib/fluvastatin combination in pilocytic astrocytoma

Background

Pilocytic astrocytomas occur predominantly in childhood. In contrast to the posterior fossa location, hypothalamo-chiasmatic pilocytic astrocytomas display a worse prognosis often leading to multiple surgical procedures and/or several lines of chemotherapy and radiotherapy to achieve long-term control. Hypothalamo-chiasmatic pilocytic astrocytomas and cerebellar pilocytic astrocytomas have a distinctive gene signature and several differential expressed genes (ICAM1, CRK, CD36, and IQGAP1) are targets for available drugs: fluvastatin and/or celecoxib.

Results

Quantification by RT-Q-PCR of the expression of these genes was performed in a series of 51 pilocytic astrocytomas and 10 glioblastomas: they were all significantly overexpressed in hypothalamo-chiasmatic pilocytic astrocytomas relative to cerebellar pilocytic astrocytomas, and CRK and ICAM1 were significantly overexpressed in pilocytic astrocytomas versus glioblastomas.

We used two commercially available glioblastoma cell lines and three pilocytic astrocytoma explant cultures to investigate the effect of celecoxib/fluvastatin alone or in combination. Glioblastoma cell lines were sensitive to both drugs and a combination of 100 μM celecoxib and 240 μM fluvastatin was the most synergistic. This synergistic combination was used on the explant cultures and led to massive cell death of pilocytic astrocytoma cells.

As a proof of concept, a patient with a refractory multifocal pilocytic astrocytoma was successfully treated with the fluvastatin/celecoxib combination used for 18 months. It was well tolerated and led to a partial tumor response.

Conclusion

This study reports evidence for new targets and synergistic effect of celecoxib/fluvastatin combination in pilocytic astrocytoma. Because it is non-toxic, this new strategy offers hope for the treatment of patients with refractory pilocytic astrocytoma.

Pathology of Spinal Ependymomas

BACKGROUND:

Ependymomas constitute approximately 40% of primary intraspinal tumors. Current World Health Organization (WHO) grading may not correlate with observed progression-free survival (PFS).

OBJECTIVE:

This retrospective study of prospectively collected data examines whether PFS is influenced by the histological grade or by the extent of resection. It also analyzes the usage and effectiveness of postoperative adjuvant radiotherapy.

METHODS:

We reviewed 134 consecutive patients with ependymomas of all grades. Pathology slides were re-reviewed and the histological grades were confirmed by a single neuropathologist. Postoperative residual or recurrence was evaluated with follow-up magnetic resonance imaging.

RESULTS:

There were 85 male and 49 female patients, ranging from 10 to 79 (median 41) years of age. Thirty patients had WHO grade I tumors, 101 had grade II tumors, and 3 had grade III tumors. Kaplan-Meier analysis of PFS demonstrated a mean duration of 6 years for grade I, 14.9 years for grade II, and 3.7 years for grade III (P &lt; .001). In grade II ependymomas, mean PFS was 11.2 years with subtotal resection and 17.8 years with gross total resection (P &lt; .01). PFS of patients who underwent subtotal resection was not significantly changed by adjuvant radiotherapy (P &lt; .36).

CONCLUSION:

Patients with grade II ependymoma have significantly longer PFS than patients with grade I ependymoma. The extent of resection did not affect PFS in grade I ependymoma but it did in grade II. Contrary to its higher grade, WHO grade II ependymoma carries a better prognosis than WHO grade I ependymoma.

Spontaneous modifications of contrast enhancement in childhood non-cerebellar pilocytic astrocytomas

INTRODUCTION

Pilocytic astrocytoma (PA) is classified by the World Health Organization as a grade I tumor. Magnetic resonance imaging (MRI) is the gold standard in the diagnosis and follow-up of this neoplasm, and assessment of contrast enhancement (CE) pattern is essential. The purpose of this study was to investigate CE changes of non-cerebellar PA (n-C PA) stable in size with serial MRI.

METHODS

Nine hundred and twelve MRI exams of 140 children with histologically proven PA were retrospectively reviewed. Patients were chosen for study inclusion if they were off therapy, without neurofibromatosis type 1, and without dimensional changes of tumor/residual tumor. In patients with CE changes, tumor size and CE size were calculated with a cross product. Descriptive statistics were calculated for continuous variables; effects of possible factors influencing changes of contrast-enhanced areas were tested.

RESULTS

Of 39 n-C PA satisfying the inclusion criteria, 12 showed CE changes in terms of appearance/increase or disappearance/decrease of CE areas. Three of these 12 PA were infratentorial and nine supratentorial. There were no significant correlations between age, gender, tumor localization, tumor size, and modification of CE areas.

CONCLUSION

In our experience, n-C PA may show variable CE over time in the absence of tumor/residual tumor dimension change. We recommend that CE fluctuations alone cannot be considered an indicator of tumor progression/regression.

Pilocytic astrocytoma: a disease with evolving molecular heterogeneity

Pilocytic astrocytoma, the most common pediatric brain tumor, is a clinically and molecularly heterogeneous disease that occurs most often in the cerebellum and hypothalamic and chiasmatic regions. Classically, pilocytic astrocytomas are driven by the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway. Recently described genetic aberrations involving this pathway are critical for tumorigenesis. Tandem duplication of 7q34 encodes BRAF and produces several KIAA1549-BRAF novel oncogenic fusions. Activating point mutations of BRAF, such as BRAF (V600E), also lead to pilocytic astrocytoma. Loss of the NF1 gene allows hyperactivation of the oncogene KRAS. In this review, we discuss the current understanding of the novel molecular aberrations described in pilocytic astrocytomas and their clinical relevance for prognosis and treatment. The prognostic indications of these aberrations are discussed with regard to tumor location, tumor pathology, and patient age. A better understanding of the evolving molecular heterogeneity of pilocytic astrocytomas offers hope for developing molecularly targeted therapeutic armamentariums.

BRAF alterations in pediatric low grade gliomas and mixed neuronal-glial tumors

Low grade astrocytomas are the most common brain tumor in children. Recent studies have identified alterations in the BRAF serine/threonine kinase gene that result in mitogen activated protein kinase pathway activation. Herewith, we investigated the genetic changes of BRAF in pediatric low grade gliomas and their relation to pathological findings and Ki-67 proliferation index. The results showed gene fusions between KIAA1549 and BRAF in 66.7 % of tumors. The majority involved the KIAA1549-BRAF exon 16-exon 9 variant. Fusion junction between KIAA1549 exon 15 and BRAF exon 9 was found in five tumors, in which the myxoid component was the predominant. This has not been previously reported. No significant correlation was found between specific KIAA1549 and BRAF fusion junctions and Ki-67 index. All of the samples included in this study were tested for the presence of the BRAF(V600E) mutation, and no positive sample was found.

To BRAF or not to BRAF: is that even a question anymore?

Alterations in BRAF have been discovered in most pediatric low-grade gliomas. Because the field has moved quickly during the past few years, there is not yet widespread awareness about what B-Raf normally does, how the BRAF gene is modified in gliomas, why mutant proteins promote gliomagenesis, and what an abnormal BRAF result means for diagnosis, prognosis, and treatment. Depending on the data from ongoing clinical trials, however, BRAF mutation screening could quickly become mandatory for all pediatric gliomas and perhaps even a subset of adult gliomas. Herein, these topics and different methods of testing for BRAF fusions and V600E point mutations are reviewed.

Something old and something new about molecular diagnostics in gliomas

Progress in our understanding of the molecular biology of neoplasms has been driven by remarkable improvements in molecular biology techniques. This has created a rapidly moving field in which even subspecialists struggle to keep abreast of the current literature. Nowhere is this more clearly demonstrated than in neuro-oncology, wherein molecular diagnostics can now wring more clinically useful information out of very small biopsies than ever before. Herein the biologic and practical aspects of four key molecular biomarkers in gliomas are discussed, including two that have been known for some time (1p/19q codeletion and EGFR amplification) as well as two whose relevance was discovered via advanced whole-genome assays (IDH1/2 mutations and BRAF alterations).

Pathological and molecular advances in pediatric low-grade astrocytoma

Pediatric low-grade astrocytomas are the most common brain tumors in children. They can have similar microscopic and clinical features, making accurate diagnosis difficult. For patients whose tumors are in locations that do not permit full resection, or those with an intrinsically aggressive biology, more effective therapies are required. Until recently, little was known about the molecular changes that drive the initiation and growth of pilocytic and other low-grade astrocytomas beyond the association of a minority of cases, primarily in the optic nerve, with neurofibromatosis type 1. Over the past several years, a wide range of studies have implicated the BRAF oncogene and other members of this signaling cascade in the pathobiology of pediatric low-grade astrocytoma. In this review, we attempt to summarize this rapidly developing field and discuss the potential for translating our growing molecular knowledge into improved diagnostic and prognostic biomarkers and new targeted therapies.

Interplay among BRAF, p16, p53, and MIB1 in pediatric low-grade gliomas

BRAF rearrangements and BRAF V600E point mutations are recurring events in pediatric low-grade gliomas. However, their clinical significance, including possible interactions between these markers and other glioma biomarkers, is unclear. In this study a retrospective cohort of 198 pediatric low-grade gliomas (including 40 treated with adjuvant therapy) was analyzed for BRAF rearrangements, BRAF V600E, p16/CDKN2A deletion, p53 expression, and MIB1 proliferation index. In tumors with BRAF rearrangement, homozygous p16 deletion correlated with shorter progression-free survival (P = .04). A high MIB1 proliferation index trended toward worse response to adjuvant radiotherapy compared to BRAF-rearranged, p16-intact tumors (P = .08). On multivariate analysis, the 2 most consistently powerful independent adverse prognostic markers were midline location (P = .0001) and p16 deletion (P = .03). Tumors with BRAF V600E had a strong trend toward an increased risk for progression (hazard ratio = 2.48, P = .07), whereas those with BRAF rearrangement had a milder trend toward reduced risk (hazard ratio = .54, P = .15). These data suggest that p16 deletion adversely impacts the outcomes of BRAF-driven gliomas, that high proliferation index may be a better marker of progression risk than BRAF, that BRAF rearrangement and BRAF V600E might not necessarily produce comparable outcomes, and that none of these markers is stronger than tumor location in determining prognosis in pediatric low-grade gliomas.