Transcriptional profiles of pilocytic astrocytoma are related to their three different locations, but not to radiological tumor features

Evaluation of KIAA1549::BRAF fusions and clinicopathological insights of pilocytic astrocytomas

BACKGROUND

Pilocytic astrocytoma (PAs) represents a significant portion of childhood primary brain tumors, with distinct histological and radiological features. The prevalence of KIAA1549::BRAF fusion in PAs has been well-established, this study aims to assess the prevalence of KIAA1549::BRAF fusions and explore their associations with tumor characteristics, radiological findings, and patient outcomes in PAs.

METHODS

Histologically confirmed cases of PAs from a 5-year period were included in the study. Demographic, histopathological, and radiological data were collected, and immunohistochemistry was performed to characterize tumor markers. FISH and qRT-PCR assays were employed to detect KIAA1549::BRAF fusions. Statistical analyses were conducted to examine associations between fusion status and various other parameters.

RESULTS

Histological analysis revealed no significant differences in tumor features based on fusion status. However, younger age groups showed higher fusion prevalence. Radiologically, fusion-positive cases were distributed across different tumor subtypes SE, CWE and NCWE. Survival analysis did not demonstrate a significant impact of fusion status on overall survival, however most cases with recurrence and death harboured KIAA1549::BRAF fusion. Of 200 PAs, KIAA1549::BRAF fusions were detected in 64 % and 74 % of cases via qRT-PCR and FISH, respectively. Concordance between the two platforms was substantial (86 %).

CONCLUSION

KIAA1549::BRAF fusions are prevalent in PAs and can be reliably detected using both FISH and qRT-PCR assays. Cost considerations suggest qRT-PCR as a more economical option for fusion detection in routine clinical practice.

Integrative multi-omics reveals two biologically distinct groups of pilocytic astrocytoma

Pilocytic astrocytoma (PA), the most common pediatric brain tumor, is driven by aberrant mitogen-activated protein kinase signaling most commonly caused by BRAF gene fusions or activating mutations. While 5-year overall survival rates exceed 95%, tumor recurrence or progression constitutes a major clinical challenge in incompletely resected tumors. Here, we used similarity network fusion (SNF) analysis in an integrative multi-omics approach employing RNA transcriptomic and mass spectrometry-based proteomic profiling to molecularly characterize PA tissue samples from 62 patients. Thereby, we uncovered that PAs segregated into two molecularly distinct groups, namely, Group 1 and Group 2, which were validated in three non-overlapping cohorts. Patients with Group 1 tumors were significantly younger and showed worse progression-free survival compared to patients with group 2 tumors. Ingenuity pathways analysis (IPA) and gene set enrichment analysis (GSEA) revealed that Group 1 tumors were enriched for immune response pathways, such as interferon signaling, while Group 2 tumors showed enrichment for action potential and neurotransmitter signaling pathways. Analysis of immune cell-related gene signatures showed an enrichment of infiltrating T Cells in Group 1 versus Group 2 tumors. Taken together, integrative multi-omics of PA identified biologically distinct and prognostically relevant tumor groups that may improve risk stratification of this single pathway driven tumor type.

The variant landscape and function of DDX3X in cancer and neurodevelopmental disorders

RNA molecules rely on proteins across their life cycle. DDX3X encodes an X-linked DEAD-box RNA helicase with a Y-linked paralog, DDX3Y. DDX3X is central to the RNA life cycle and is implicated in many conditions, including cancer and the neurodevelopmental disorder DDX3X syndrome. DDX3X-linked conditions often exhibit sex differences, possibly due to differences between expression or function of the X- and Y-linked paralogs DDX3X and DDX3Y. DDX3X-related diseases have different mutational landscapes, indicating different roles of DDX3X. Understanding the role of DDX3X in normal and disease states will inform the understanding of DDX3X in disease. We review the function of DDX3X and DDX3Y, discuss how mutation type and sex bias contribute to human diseases involving DDX3X, and review possible DDX3X-targeting treatments.

Detection and genomic analysis of BRAF fusions in Juvenile Pilocytic Astrocytoma through the combination and integration of multi-omic data

BACKGROUND

Juvenile Pilocytic Astrocytomas (JPAs) are one of the most common pediatric brain tumors, and they are driven by aberrant activation of the mitogen-activated protein kinase (MAPK) signaling pathway. RAF-fusions are the most common genetic alterations identified in JPAs, with the prototypical KIAA1549-BRAF fusion leading to loss of BRAF's auto-inhibitory domain and subsequent constitutive kinase activation. JPAs are highly vascular and show pervasive immune infiltration, which can lead to low tumor cell purity in clinical samples. This can result in gene fusions that are difficult to detect with conventional omics approaches including RNA-Seq.

METHODS

To this effect, we applied RNA-Seq as well as linked-read whole-genome sequencing and in situ Hi-C as new approaches to detect and characterize low-frequency gene fusions at the genomic, transcriptomic and spatial level.

RESULTS

Integration of these datasets allowed the identification and detailed characterization of two novel BRAF fusion partners, PTPRZ1 and TOP2B, in addition to the canonical fusion with partner KIAA1549. Additionally, our Hi-C datasets enabled investigations of 3D genome architecture in JPAs which showed a high level of correlation in 3D compartment annotations between JPAs compared to other pediatric tumors, and high similarity to normal adult astrocytes. We detected interactions between BRAF and its fusion partners exclusively in tumor samples containing BRAF fusions.

CONCLUSIONS

We demonstrate the power of integrating multi-omic datasets to identify low frequency fusions and characterize the JPA genome at high resolution. We suggest that linked-reads and Hi-C could be used in clinic for the detection and characterization of JPAs.

The Transcriptomic Landscape of Pediatric Astrocytoma

Central nervous system tumors are the most common solid neoplasia during childhood and represent one of the leading causes of cancer-related mortality. Tumors arising from astrocytic cells (astrocytomas) are the most frequently diagnosed, and according to their histological and pathological characteristics, they are classified into four categories. However, an additional layer of molecular classification considering the DNA sequence of the tumorigenesis-associated genes IDH1/2 and H3F3A has recently been incorporated into the classification guidelines. Although mutations in H3F3A are found exclusively in a subtype of grade IV pediatric astrocytoma, mutations in IDH1/2 genes are very rare in children under 14 years of age. The transcriptomic profiles of astrocytoma in adults and children have been extensively studied. However, there is scarce information on these profiles in pediatric populations considering the status of tumorigenesis-associated genes. Therefore, here we report the transcriptomic landscape of the four grades of pediatric astrocytoma by RNA sequencing. We found several well-documented biological functions associated with the misregulated genes in the four grades of astrocytoma, as well as additional biological pathways. Among the four grades of astrocytoma, we found shared misregulated genes that could have implications in tumorigenesis. Finally, we identified a transcriptional signature for almost all grades of astrocytoma that could be used as a transcription-based identification method.

A Toolkit for Profiling the Immune Landscape of Pediatric Central Nervous System Malignancies

The prognosis of pediatric central nervous system (CNS) malignancies remains dismal due to limited treatment options, resulting in high mortality rates and long-term morbidities. Immunotherapies, including checkpoint inhibition, cancer vaccines, engineered T cell therapies, and oncolytic viruses, have promising results in some hematological and solid malignancies, and are being investigated in clinical trials for various high-grade CNS malignancies. However, the role of the tumor immune microenvironment (TIME) in CNS malignancies is mostly unknown for pediatric cases. In order to successfully implement immunotherapies and to eventually predict which patients would benefit from such treatments, in-depth characterization of the TIME at diagnosis and throughout treatment is essential. In this review, we provide an overview of techniques for immune profiling of CNS malignancies, and detail how they can be utilized for different tissue types and studies. These techniques include immunohistochemistry and flow cytometry for quantifying and phenotyping the infiltrating immune cells, bulk and single-cell transcriptomics for describing the implicated immunological pathways, as well as functional assays. Finally, we aim to describe the potential benefits of evaluating other compartments of the immune system implicated by cancer therapies, such as cerebrospinal fluid and blood, and how such liquid biopsies are informative when designing immune monitoring studies. Understanding and uniformly evaluating the TIME and immune landscape of pediatric CNS malignancies will be essential to eventually integrate immunotherapy into clinical practice.

Risk of second primary neoplasms of the central nervous system

Purpose

Second primary (SP) neoplasms of the central nervous system (CNS) among cancer survivors are devastating but poorly understood processes. The absolute risk, or true incidence, of developing an SP CNS tumor among cancer survivors is not well characterized.

Methods and Materials

Patients diagnosed with cancer between 1975 and 2016 were queried using the Surveillance, Epidemiology, and End Results Program. Cumulative incidence rates (CIRs) were estimated using competitive risk analysis. The effects of covariates were assessed using multivariate competitive risk regression.

Results

More than 3.8 million patient records were extracted. The absolute risk of developing an SP CNS neoplasm at 25 years was highest among long-term survivors of CNS cancers (CIR, 6.6%). Cranial radiation increased the incidence of SP tumors in pediatric patients (25-year CIR, 5.7% vs 1.1%; P = .0012) but not adults (25-year CIR, 5.8% vs 5.0%; P = .66). Multivariate cumulative risk regression identified radiation among pediatric patients as the greatest risk for an increased CIR (subdistribution hazard ratio, 2.50; 95% CI, 1.86-3.38; P = 2e-9). Meningiomas (42.9% vs 24.1%; P = 2e-7) and glioblastomas (20.5% vs 14.5%; P = .046) represented a greater proportion of the SP CNS tumors in those who received cranial irradiation. The median age of an SP diagnosis was decreased among those who received prior radiation (41 years [interquartile range (IQR), 30-65 years] vs 49 years [IQR, 30-65 years]; P = 7e-5).

Conclusions

The risk of developing a second primary CNS neoplasm is elevated in patients with a prior CNS cancer independent of treatment history. The association between cranial radiation therapy and risk for subsequent cancers may be limited to the pediatric population.

Glioma-Targeted Therapeutics: Computer-Aided Drug Design Prospective

Amongst the several types of brain cancers known to humankind, glioma is one of the most severe and life-threatening types of cancer, comprising 40% of all primary brain tumors. Recent reports have shown the incident rate of gliomas to be 6 per 100,000 individuals per year globally. Despite the various therapeutics used in the treatment of glioma, patient survival rate remains at a median of 15 months after undergoing first-line treatment including surgery, radiation, and chemotherapy with Temozolomide. As such, the discovery of newer and more effective therapeutic agents is imperative for patient survival rate. The advent of computer-aided drug design in the development of drug discovery has emerged as a powerful means to ascertain potential hit compounds with distinctively high therapeutic effectiveness against glioma. This review encompasses the recent advances of bio-computational in-silico modeling that have elicited the discovery of small molecule inhibitors and/or drugs against various therapeutic targets in glioma. The relevant information provided in this report will assist researchers, especially in the drug design domains, to develop more effective therapeutics against this global disease.

Pilocytic astrocytoma demethylation and transcriptional landscapes link bZIP transcription factors to immune response

BACKGROUND

Pilocytic astrocytoma (PA) is the most common pediatric brain tumor. While genome and transcriptome landscapes are well studied, data of the complete methylome, tumor cell composition, and immune infiltration are scarce.

METHODS

We generated whole genome bisulfite sequence (WGBS) data of 9 PAs and 16 control samples and integrated available 154 PA and 57 control methylation array data. RNA sequence data of 49 PAs and 11 control samples as well as gene expression arrays of 248 PAs and 28 controls were used to assess transcriptional activity.

RESULTS

DNA-methylation patterns of partially methylated domains suggested high stability of the methylomes during tumorigenesis. Comparing tumor and control tissues of infra- and supratentorial location using methylation arrays revealed a site specific pattern. Analysis of WGBS data revealed 9381 significantly differentially methylated regions (DMRs) in PA versus control tissue. Enhancers and transcription factor (TF) motifs of five distinct TF families were found to be enriched in DMRs. Methylation together with gene expression data-based in silico tissue deconvolution analysis indicated a striking variation in the immune cell infiltration in PA. A TF network analysis showed a regulatory relation between basic leucine zipper (bZIP) transcription factors and genes involved in immune-related processes.

CONCLUSION

We provide evidence for a link of focal methylation differences and differential gene expression to immune infiltration.

In silico analysis identifies a putative cell-of-origin for BRAF fusion-positive cerebellar pilocytic astrocytoma

Childhood cancers are increasingly recognized as disorders of cellular development. This study sought to identify the cellular and developmental origins of cerebellar pilocytic astrocytoma, the most common brain tumor of childhood. Using publicly available gene expression data from pilocytic astrocytoma tumors and controlling for driver mutation, a set of developmental-related genes which were overexpressed in cerebellar pilocytic astrocytoma was identified. These genes were then mapped onto several developmental atlases in order to identify normal cells with similar gene expression patterns and the developmental trajectory of those cells was interrogated. Eight known neuro-developmental genes were identified as being expressed in cerebellar pilocytic astrocytoma. Mapping those genes or their orthologs onto mouse neuro-developmental atlases identified overlap in their expression within the ventricular zone of the cerebellar anlage. Further analysis with a single cell RNA-sequencing atlas of the developing mouse cerebellum defined this overlap as occurring in ventricular zone progenitor cells at the division point between GABA-ergic neuronal and glial lineages, a developmental trajectory which closely mirrors that previously described to occur within pilocytic astrocytoma cells. Furthermore, ventricular zone progenitor cells and their progeny exhibited evidence of MAPK pathway activation, the paradigmatic oncogenic cascade known to be active in cerebellar pilocytic astrocytoma. Gene expression from developing human brain atlases recapitulated the same anatomic localizations and developmental trajectories as those found in mice. Taken together, these data suggest this population of ventricular zone progenitor cells as the cell-of-origin for BRAF fusion-positive cerebellar pilocytic astrocytoma.

NF-кB inhibition by DHMEQ: in vitro antiproliferative effects on pilocytic astrocytoma and concise review of the current literature

INTRODUCTION

Pilocytic astrocytoma (PA) is the most common brain tumor that affects the pediatric population. Even though PA is benign and treatment only involves surgery, recurrent or unresectable tumors require chemo- and radiotherapy. Besides BRAF, CDKN2A, or IDH mutations, the hyperactivation of the nuclear factor NF-κB contributes to tumor growth and survival.

METHODS

In the present study, we used publicly available data for the in silico analysis of NF-κB subunits (RELA, RELB, REL, NF-κB1, and NF-κB2) expression in PA samples. Besides, in vitro assays were performed to evaluate proliferation, migration, cell death, on the PA cell line Res286 comparing to human primary astrocytes. Sensitization to radiation therapy and temozolomide (TMZ) was also assayed.

RESULTS

Our results showed that all the members of the NF-kB family are upregulated in PA datasets compared to normal brain tissues. Moreover, DHMEQ treatment significantly reduced cell growth and motility, while sensitized cells to ionizing radiation and TMZ, as previously seen in high-grade gliomas.

CONCLUSIONS

This drug presents a potential application in clinical practice for the treatment of recurrent or inoperable PA. Moreover, its use might assist adjuvant chemotherapy and reduce irradiation doses to avoid toxicity to the surrounding tissues.

The Role of Contactin 1 in Cancers: What We Know So Far

Cancers are among the difficult-to-treat diseases despite advances in diagnosis and treatment. Although newer effective targets remain to be discovered, targeted therapy has emerged as a promising field. In the last decade, contactin 1 (CNTN1) has surfaced as an important cancer-related molecule. CNTN1 is a neuronal membrane glycoprotein, which, if overexpressed, is found in different cancer cell lines, cancer tissues, and transgenic mice. It is positively associated with lymphatic invasion, metastasis, late TNM stage, and a short overall survival time. However, the role of CNTN1 in cancer cell proliferation remains unclear. In addition, CNTN1 is involved in cancer cell invasion, migration, metastasis, and chemoresistance by promoting epithelial-mesenchymal transition and mediating several signal transduction pathways. Several studies suggest CNTN1 as a new therapeutic target for cancers. This review aims to summarize the research developments on CNTN1 in various cancers, to establish its role in epithelial-mesenchymal transition and signal transduction pathways, and to identify promising areas for further investigation.

Effect of radiation therapy on overall survival following subtotal resection of adult pilocytic astrocytoma

OBJECTIVE

Pilocytic astrocytoma (PCA) is a low-grade glioma that primarily presents in children, but can also present in adulthood. Ideal primary treatment for PCA is gross total resection. However, for patients who are only able to undergo subtotal resection, the optimal course of post-operative therapy remains unclear. We investigated the association of patient characteristics and radiation therapy (RT) with overall survival specifically for adult PCA patients who underwent subtotal tumor resection.

METHODS

Information on adult patients (age ≥18 years old) who underwent subtotal PCA resection between 2004 and 2016 was collected from the National Cancer Database (NCDB). A multivariate Cox proportional hazards model was utilized to determine factors associated with overall survival.

RESULTS

A total of 451 patients were identified. The mean age of our patient cohort was 36.8 years old, and the majority of patients (83.4%) did not receive RT following subtotal PCA resection. Overall median survival was >93.8 months. On multivariate analysis, patients who were older at diagnosis (hazard ratio [HR] = 1.04, 95% confidence interval [CI] = 1.02-1.06, p < 0.01), black (HR = 2.35, CI = 1.05-5.23, p = 0.037), had a Charlson/Deyo comorbidity score ≥ 1 (HR = 2.27, CI = 1.00-5.14, p = 0.049), or received RT during their initial treatment (HR = 3.77, CI = 1.77-8.03, p < 0.01) had a significantly higher risk of death following subtotal PCA resection.

CONCLUSION

Post-operative RT was associated with a significantly higher risk of death among adults who underwent subtotal PCA resection. Our findings provide support for further inquiry into the efficacy of RT within this patient population.

Tectal Low-Grade Glioma with H3 K27M Mutation

BACKGROUND

In the revised World Health Organization 2016 classification of central nervous system tumors, "diffuse midline glioma, H3 K27M-mutant" has been added as a new diagnostic entity. However, some confusion exists concerning this diagnostic entity because H3 K27M-mutant diffuse midline glioma is diagnosed with grade IV regardless of morphologic phenotype. Furthermore, the significance of H3 K27M mutation in tumors that aren't typical "diffuse midline glioma, H3 K27M-mutant," such as those with an unusual location and nontypical histology, remains unclear.

CASE DESCRIPTION

To elucidate further such unusual tumors, we describe here a rare case of pediatric low-grade glioma located in the tectum, which was morphologically a pilocytic astrocytoma (PA) with genetically H3 K27M mutation but no microvascular proliferation, necrosis, mitoses, or other genetic alterations, insofar as we were able to observe. At the latest follow-up, 28 months after surgery, radiotherapy, and chemotherapy, the patient was found to be free from any neurologic deficits and MRI demonstrated that the tumor was stable without tumor regrowth. This case might be identified as "diffuse midline glioma, H3 K27M-mutant", grade IV, when applying only the current World Health Organization 2016 classification. In addition, we discuss the morphologically benign gliomas harboring the H3 K27M mutation based on the literature.

CONCLUSIONS

We describe here a rare case and present a short literature review of circumscribed/nondiffuse gliomas, particularly in PA with H3 K27M mutation. However, the significance of H3 K27M mutation for PA remains unclear, so further studies and clinical data are needed to elucidate the biology and optimal treatment of such tumors.

A Novel Prognostic Signature of Transcription Factors for the Prediction in Patients With GBM

Background: Although the diagnosis and treatment of glioblastoma (GBM) is significantly improved with recent progresses, there is still a large heterogeneity in therapeutic effects and overall survival. The aim of this study is to analyze gene expressions of transcription factors (TFs) in GBM so as to discover new tumor markers.

Methods: Differentially expressed TFs are identified by data mining using public databases. The GBM transcriptome profile is downloaded from The Cancer Genome Atlas (TCGA). The nonnegative matrix factorization (NMF) method is used to cluster the differentially expressed genes to discover hub genes and signal pathways. The TFs affecting the prognosis of GBM are screened by univariate and multivariate COX regression analysis, and the receiver operating characteristic (ROC) curve is determined. The GBM hazard model and nomogram map are constructed by integrating the clinical data. Finally, the TFs involving potential signaling pathways in GBM are screened by Gene Set Enrichment Analysis (GSEA), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis.

Results: There are 68 differentially expressed TFs in GBM, of which 43 genes are upregulated and 25 genes are downregulated. NMF clustering analysis suggested that GBM patients are divided into three groups: Clusters A, B, and C. LHX2, MEOX2, SNAI2, and ZNF22 are identified from the above differential genes by univariate/multivariate regression analysis. The risk score of those four genes are calculated based on the beta coefficient of each gene, and we found that the predictive ability of the risk score gradually increased with the prolonged predicted termination time by time-dependent ROC curve analysis. The nomogram results have showed that the integration of risk score, age, gender, chemotherapy, radiotherapy, and 1p/19q can further improve predictive ability towards the survival of GBM. The pathways in cancer, phosphoinositide 3-kinases (PI3K)–Akt signaling, Hippo signaling, and proteoglycans, are highly enriched in high-risk groups by GSEA. These genes are mainly involved in cell migration, cell adhesion, epithelial–mesenchymal transition (EMT), cell cycle, and other signaling pathways by GO and KEGG analysis.

Conclusion: The four-factor combined scoring model of LHX2, MEOX2, SNAI2, and ZNF22 can precisely predict the prognosis of patients with GBM.

Characteristics, survival and incidence rates and trends of pilocytic astrocytoma in children in the United States; SEER-based analysis

INTRODUCTION

Pilocytic astrocytoma (PA) is a neurological neoplasm and a common neurological tumor among children. No recent reports have studied the recent demographic characteristics of PA cases in the US.

METHODOLOGY

We used the Surveillance, Epidemiology, and End Results (SEER) Program to retrieve data on children diagnosed with PA between 2000 and 2015. We calculated the incidence, annual percentage changes (APC), and survival.

RESULTS

Our study included 3084 children with PA, with an incidence of 8.227 per 1,000,000 person-years, being highest among whites (9.062), and children aged 1-4 year (11.175). Overall incidence in children increased significantly over the study period, with an APC of 0.825% (95% CI[0.027-1.630], P = .044). Moreover, incidence among blacks increased significantly over the study period (APC = 3.466%, 95% CI[0.342-6.688], P = .032), but did not change among other races. The relative 5-year survival of included patients was 95.3%, with patients younger than 1 year having the worst survival.

CONCLUSIONS

Overall PA incidence and incidence among blacks has been increasing last decade. Additionally, PA survival was found to be worse among infants. Further studies are also needed to investigate the effect of the age and race on the incidence and survival of PA.

Integrated DNA methylation analysis identifies topographical and tumoral biomarkers in pilocytic astrocytomas

Pilocytic astrocytoma (PA) is the most common glioma in pediatric patients and occurs in different locations. Chromosomal alterations are mostly located at chromosome 7q34 comprising the BRAF oncogene with consequent activation of the mitogen-activated protein kinase pathway. Although genetic and epigenetic alterations characterizing PA from different localizations have been reported, the role of epigenetic alterations in PA development is still not clear. The aim of this study was to investigate whether distinctive methylation patterns may define biologically relevant groups of PAs. Integrated DNA methylation analysis was performed on 20 PAs and 4 normal brain samples by Illumina Infinium HumanMethylation27 BeadChips.

We identified distinct methylation profiles characterizing PAs from different locations (infratentorial vs supratentorial) and tumors with onset before and after 3 years of age. These results suggest that PA may be related to the specific brain site where the tumor arises from region-specific cells of origin. We identified and validated in silico the methylation alterations of some CpG islands. Furthermore, we evaluated the expression levels of selected differentially methylated genes and identified two biomarkers, one, IRX2, related to the tumor localization and the other, TOX2, as tumoral biomarker.

A new NFIA:RAF1 fusion activating the MAPK pathway in pilocytic astrocytoma

Pilocytic astrocytoma (PA) is one of the most common brain cancers among children and activation of the Mitogen-Activated Protein Kinase (MAPK) pathway is considered the hallmark. In the majority of cases, oncogenic BRAF fusions or BRAF V600E mutations are observed, while RAF1 or NF1 alterations are more rarely found. However, in some cases, no apparent cancer driver events can be identified. Here, we describe a novel fusion between the transcription factor nuclear factor 1A (NFIA) and Raf-1 proto-oncogene (RAF1) in a 5-year old boy with PA. The novel fusion was identified as part of a comprehensive genomic tumor profiling. We show that the NFIA:RAF1 fusion results in constitutive Raf1 kinase activity, leading to activation of downstream MEK1/2 cascade and increased proliferation of cancer cells. The NFIA:RAF1 fusion displayed distinct subcellular localization towards the plasma membrane indicative of Raf-1 activation, in contrast to both wild type NFIA and Raf-1, which were localized in the nucleus and cytoplasm, respectively. In conclusion, our data support the existence of rare oncogenic RAF1 fusions with constitutive Raf-1 activity. This highlights the need for broad genetic testing in order to refine diagnostics of PA and to unravel potential treatment options, e.g. with MEK inhibitors.