Clinical progression, pathological characteristics, and radiological findings in children with diffuse leptomeningeal glioneuronal tumors: A systematic review

Novel insights toward diagnosis and treatment of glioneuronal and neuronal tumors in young adults

Aim: Glioneuronal and neuronal tumors are rare primary central nervous system malignancies with heterogeneous features. Due to the rarity of these malignancies diagnosis and treatment remains a clinical challenge. Methods: Here we performed a narrative review aimed to investigate the principal issues concerning the diagnosis, pathology, and clinical management of glioneuronal tumors. Results: Diagnostic criteria have been recently overturned thanks to a better characterization on a histological and molecular biology level. The study of genomic alterations occurring within these tumors has allowed us to identify potential therapeutic targets including BRAF, FGFR, and PDGFRA. Conclusion: Techniques allowing molecular sequencing DNA methylation assessment of the disease are essential diagnostic tools. Targeting agents should be included in the therapeutic armamentarium after loco-regional treatment failure.

Pediatric Meningeal Diseases: What Radiologists Need to Know

Evaluating altered mental status and suspected meningeal disorders in children often begins with imaging, typically before a lumbar puncture. The challenge is that meningeal enhancement is a common finding across a range of pathologies, making diagnosis complex. This review proposes a categorization of meningeal diseases based on their predominant imaging characteristics. It includes a detailed description of the clinical and imaging features of various conditions that lead to leptomeningeal or pachymeningeal enhancement in children and adolescents. These conditions encompass infectious meningitis (viral, bacterial, tuberculous, algal, and fungal), autoimmune diseases (such as anti-MOG demyelination, neurosarcoidosis, Guillain-Barré syndrome, idiopathic hypertrophic pachymeningitis, and NMDA-related encephalitis), primary and secondary tumors (including diffuse glioneuronal tumor of childhood, primary CNS rhabdomyosarcoma, primary CNS tumoral metastasis, extracranial tumor metastasis, and lymphoma), tumor-like diseases (Langerhans cell histiocytosis and ALK-positive histiocytosis), vascular causes (such as pial angiomatosis, ANCA-related vasculitis, and Moyamoya disease), and other disorders like spontaneous intracranial hypotension and posterior reversible encephalopathy syndrome. Despite the nonspecific nature of imaging findings associated with meningeal lesions, narrowing down the differential diagnoses is crucial, as each condition requires a tailored and specific treatment approach.

Imaging of pediatric glioneuronal and neuronal tumors

Glioneuronal tumors (GNTs) are an expanding group of primary CNS neoplasms, commonly affecting children, adolescents and young adults. Most GNTs are relatively indolent, low-grade, WHO grade I lesions. In the pediatric age group, GNTs have their epicenter in the cerebral cortex and present with seizures. Alterations in the mitogen-activated protein kinase (MAPK) pathway, which regulates cell growth, are implicated in tumorigenesis. Imaging not only plays a key role in the characterization and pre-surgical evaluation of GNTs but is also crucial role in follow-up, especially with the increasing use of targeted inhibitors and immunotherapies. In this chapter, we review the clinical and imaging perspectives of common pediatric GNTs.

Paediatric low-grade glioma: the role of classical pathology in integrated diagnostic practice

Low-grade gliomas are a cause of severe and often life-long disability in children. Pathology plays a key role in their management by establishing the diagnosis, excluding malignant alternatives, predicting outcomes and identifying targetable genetic alterations. Molecular diagnosis has reshaped the terrain of pathology, raising the question of what part traditional histology plays. In this review, we consider the classification and pathological diagnosis of low-grade gliomas and glioneuronal tumours in children by traditional histopathology enhanced by the opportunities afforded by access to comprehensive genetic and epigenetic characterisation.

The potential of liquid biopsy for detection of the KIAA1549-BRAF fusion in circulating tumor DNA from children with pilocytic astrocytoma

Background

Low-grade gliomas (LGGs) represent children's most prevalent central nervous system tumor, necessitating molecular profiling to diagnose and determine the most suitable treatment. Developing highly sensitive screening techniques for liquid biopsy samples is particularly beneficial, as it enables the early detection and molecular characterization of tumors with minimally invasive samples.

Methods

We examined CSF and plasma samples from patients with pilocytic astrocytoma (PA) using custom multiplexed droplet digital polymerase chain reaction (ddPCR) assays based on whole genome sequencing data. These assays included a screening test to analyze BRAF duplication and a targeted assay for the detection of patient-specific KIAA1549::BRAF fusion junction sequences or single nucleotide variants.

Results

Our findings revealed that 5 out of 13 individual cerebrospinal fluid (CSF) samples tested positive for circulating tumor DNA (ctDNA). Among these cases, 3 exhibited the KIAA1549::BRAF fusion, which was detected through copy number variation (CNV) analysis (n = 1) or a fusion-specific probe (n = 2), while 1 case each displayed the BRAF V600E mutation and the FGFR1 N577K mutation. Additionally, a quantitative analysis of cell-free DNA (cfDNA) concentrations in PA CSF samples showed that most cases had low cfDNA levels, below the limit of detection of our assay (<1.9 ng).

Conclusions

While CNV analysis of CSF samples from LGGs still has some limitations, it has the potential to serve as a valuable complementary tool. Furthermore, it can also be multiplexed with other aberrations, for example, to the BRAF V600 test, to provide important insights into the molecular characteristics of LGGs.

Diffuse Leptomeningeal Glioneuronal Tumor: First Description of Metastasis to the Lung and Bone Marrow

Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a rare neoplasm of the central nervous system (CNS) that primarily affects the leptomeninges. However, it can also involve the brain parenchyma and spinal cord. We report the first case of metastasis of this primary CNS tumor to the lung and bone marrow. An 18-year-old male was diagnosed with DLGNT through meningeal biopsy after multiple events of transient neurologic signs and symptoms that included recurrent episodes of encephalopathy, seizures, cerebral vasospasms, cranial nerve palsy, and urinary dysfunction. Five months after diagnosis, the patient presented with pancytopenia and pulmonary effusion. At that time, he was being treated with temozolomide, after radiation treatment to the brain and spinal cord. Bone marrow biopsy and pleural cytology revealed systemic metastases from the primary CNS tumor. He was then treated with chemotherapy with carboplatin and vincristine which improved his condition for two and a half months. Unfortunately, the patient died of a high systemic metastatic burden. Primary CNS tumors rarely produce systemic metastases, and this is the first report of DLGNT with bone marrow and pulmonary metastases. Chemotherapy with carboplatin and vincristine should be considered as a treatment for patients with DLGNT, as the patient presented a systemic response with clinical and radiological improvement.

Aggressive Diffuse Leptomeningeal Glioneuronal Tumor in a Pediatric Patient Presenting With Mismatch Repair Gene Mutations

Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a rare primary central nervous system tumor. We present the case of a five-year-old male patient with a rapid progression of a thoracic DLGNT. Initial presentation and workup confirmed acute communicating hydrocephalus requiring a ventriculoperitoneal shunt. Cerebrospinal fluid analysis showed hyperproteinorrachia. Additional workup demonstrated an intramedullary mass at the conus medullaris associated with leptomeningeal enhancement. A T10-T12 laminoplasty with tumor resection was performed. Immunohistochemistry was positive for glial fibrillary acid protein and synaptophysin, with a negative epithelial membrane antigen. The tumor had a Ki67 proliferation index of 9%. Gene tumor analysis revealed the presence of the KIAA1549-BRAF gene fusion. The tumor expressed MSH6, MLH1, MSH2, and PMS2 mismatch repair gene mutations. Multiple subsequent shunt revisions were performed due to malfunction secondary to the hyperproteinorrachia. Follow-up studies showed extensive brain and spinal nodular cystic lesions associated with extensive leptomeningeal spread of disease. The patient received chemotherapy but died due to disease progression. This case report described a rapidly progressive and aggressive DLGNT in a pediatric patient presenting mismatch repair gene mutations. Due to hyperproteinorrachia, shunt revisions are frequently needed in these patients. Even though DLGNT pathology can depict a low-grade tissue, some tumors behave aggressively with minimal significant response to medical and surgical treatments. Mutations of mismatch repair genes MSH6, MLH1, MSH2, and PMS2 may be associated with more aggressive tumors.