A DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOR IN THE AREA OF THE CAUDATE NUCLEUS IN A 57-YEAR-OLD WOMAN

Septal dysembryoplastic neuroepithelial tumor: a comprehensive clinical, imaging, histopathologic, and molecular analysis

BACKGROUND

Dysembryoplastic neuroepithelial tumors (DNETs) are uncommon neural tumors presenting most often in children and young adults and associated with intractable seizures. Rare midline neoplasms with similar histological features to those found in DNETs have been described near the septum pellucidum and termed "DNET-like neoplasms of the septum pellucidum." Due to their rarity, these tumors have been described in just a few reports and their genetic alterations sought only in small series.

METHODS

We collected 20 of these tumors for a comprehensive study of their clinical, radiological, and pathological features. RNA sequencing or targeted DNA sequencing was undertaken on 18 tumors, and genome-wide DNA methylation profiling was possible with 11 tumors. Published cases (n = 22) were also reviewed for comparative purposes.

RESULTS

The commonest presenting symptoms and signs were related to raised intracranial pressure; 40% of cases required cerebrospinal fluid diversion. Epilepsy was seen in approximately one third of cases. All patients had an indolent disease course, despite metastasis within the neuraxis in a few cases. Radiologically, the septum verum/septal nuclei were involved in all cases and are the proposed site of origin for septal DNET (sDNET). Septal DNET showed a high frequency (~80%) of mutations of platelet derived growth factor receptor A (PDGFRA), and alterations in fibroblast growth factor receptor 1 (FGFR1) and neurofibromatosis type 1 (NF1) were also identified. In a genomic DNA methylation analysis alongside other neural tumors, sDNETs formed a separate molecular group.

CONCLUSIONS

Genetic alterations that are different from those of cerebral DNETs and a distinct methylome profile support the proposal that sDNET is a distinct disease entity.

Myxoid glioneuronal tumor, PDGFRA p.K385-mutant: clinical, radiologic, and histopathologic features

"Myxoid glioneuronal tumor, PDGFRA p.K385-mutant" is a recently described tumor entity of the central nervous system with a predilection for origin in the septum pellucidum and a defining dinucleotide mutation at codon 385 of the PDGFRA oncogene replacing lysine with either leucine or isoleucine (p.K385L/I). Clinical outcomes and optimal treatment for this new tumor entity have yet to be defined. Here, we report a comprehensive clinical, radiologic, and histopathologic assessment of eight cases. In addition to its stereotypic location in the septum pellucidum, we identify that this tumor can also occur in the corpus callosum and periventricular white matter of the lateral ventricle. Tumors centered in the septum pellucidum uniformly were associated with obstructive hydrocephalus, whereas tumors centered in the corpus callosum and periventricular white matter did not demonstrate hydrocephalus. While multiple patients were found to have ventricular dissemination or local recurrence/progression, all patients in this series remain alive at last clinical follow-up despite only biopsy or subtotal resection without adjuvant therapy in most cases. Our study further supports "myxoid glioneuronal tumor, PDGFRA p.K385-mutant" as a distinct CNS tumor entity and expands the spectrum of clinicopathologic and radiologic features of this neoplasm.

Dysembryoplastic Neuroepithelial Tumor of the Septum Pellucidum and the Supratentorial Midline: Histopathologic, Neuroradiologic, and Molecular Features of 7 Cases

Dysembryoplastic neuroepithelial tumors (DNTs) are one of the most common epilepsy-associated low-grade glioneuronal tumors of the central nervous system. Although most DNTs occur in the cerebral cortex, DNT-like tumors with unusual intraventricular or periventricular localizations have been reported. Most of them involve the septum pellucidum and the foramen of Monro. In this study, we have described the neuroradiologic, histopathologic, and molecular features of 7 cases (4 female and 3 male; patient age range, 3 to 34 y; mean age, 16.7 y). The tumors, all localized near the supratentorial midline structures in proximity to the foramen of Monro and septum pellucidum, appeared in magnetic resonance imaging as well-delimited cystic lesions with cerebrospinal fluid-like signal on T1-weighted and T2-weighted images, some of them with typical fluid-attenuated inversion recovery ring sign. Histologically, they shared features with classic cortical DNTs but did not display aspects of multinodularity. From a molecular point of view the cases investigated did not show KIAA1549-BRAF fusions or FGFR1 mutations, alterations otherwise observed in pilocytic astrocytomas, or MYB and MYBL1 alterations that have been identified in a large group of pediatric low-grade gliomas. Moreover, BRAF mutations, which so far represent the most common molecular alteration found in cortical DNTs, were absent in this group of rare periventricular tumors.

Dysembryoplastic neuroepithelial tumor: a clinical, neuroradiological, and pathological study of 15 cases

Dysembryoplastic neuroepithelial tumors are rare, surgically curable, neuronal-glial neoplasms affecting young patients with intractable epilepsy. Its recognition is needed to avoid unnecessary adjuvant therapy. The authors reviewed the records of 15 patients with dysembryoplastic neuroepithelial tumors who underwent epilepsy surgery using intraoperative electrocorticography monitoring, including 8 males and 7 females (mean age, 15.8 years). Neuroimaging showed a predominantly intracortical location, the presence of septations, a triangular pattern of distribution, a lack of contrast enhancement, and an absence of peritumoral edema. Eleven cases were classified as complex type, 3 as simple type, and 1 as "nonspecific" type. Associated cortical dysplasia was found in 5 cases and leptomeningeal involvement in 1 case. Its immunophenotype suggested a pluripotential neuroepithelial origin. The mean follow-up was 37.5 months; 2 patients had tumor recurrence. Although they are generally benign neoplasms, recurrences sometimes occur. Complete resection of the tumor with the epileptogenic zone is important for a favorable outcome.

Focal epilepsy associated with dysembryoplastic neuroepithelial tumor in the area of the caudate nucleus

Dysembryoplastic neuroepithelial tumors (DNTs) are usually located within the supratentorial cortex, often in the temporal lobe and they are frequently associated with intractable complex partial seizures. DNTs in extracortical sites are rare. Thus far, 21 cases of 36 DNT-lesions occurring in these areas have been reported; only 8 out of them had epilepsy. We report a case of a 39-year-old woman who had pharmacoresistant epilepsy associated to a DNT in the caudate nucleus-periventricular area treated by lesionectomy. During a 4-year follow-up period, the patient was seizure free and the tumor did not recur. We discuss the hypothetical epileptogenic mechanism involved and we review the pertinent literature.

Intraventricular dysembryoplastic neuroepithelial tumour: case report

Dysembryoplastic neuroepithelial tumour (DNT) is located in the cerebral cortex with very few exceptions. In this article, an extremely rare case of intraventricular DNT originating from the septum pellucidum is reported. A 25-year-old woman presented with 5-month history of headache. Cranial magnetic resonance imaging (MRI) scans revealed a mass in the right lateral and third ventricle which was hypointense on T1-weighted image, and hyperintense on T2-weighted images. No contrast enhancement was detected. The lesion was excised totally using a transcallosal-transventricular approach. Immunohistochemical examination revealed DNT. The patient was discharged without any neurological deficits. Intraventricular DNT presents with symptoms of increased intracranial pressure rather than seizures. Distinguishing DNT from other intraventricular tumours is essential as DNT is characterized by benign clinical course and does not require adjuvant therapy.

Intraventricular dysembryoplastic neuroepithelial tumor in a pediatric patient: is it the most common extracortical location for DNT?

Dysembryoplastic neuroepithelial tumor (DNT) is commonly located in the supratentorial cortex. Extracortical localization of DNT is extremely rare. A 15-year-old female presented with loss of consciousness after head trauma. MRI demonstrated hydrocephalus secondary to a small non-enhancing T1 hypointense and T2 hyperintense mass lesion in the foramen of Monro; with radiologic impression of low-grade astrocytoma or colloid cyst. Tumor was gross totally resected. Histologic examination showed partly microcystic architecture with oligodendroglia-like neurocytic cells, glioneuronal element, and floating neurons, with synaptophysin reactivity mainly in cell processes, consistent with DNT. Focal subependymoma-like pattern was noted. The low tumor cellularity and morphologic pattern did not support a central neurocytoma. Patient was asymptomatic and was radiologically stable 9 months post-surgery. Literature review of previously reported supratentorial extracortical DNT cases demonstrate that 24 of 25 cases involved the ventricular system (as in our case) of which eight additionally involved periventricular deep gray or white matter. None of the cases recurred following surgery. Clinico-pathologically, extracortical DNTs were similar to the cerebral cortical simple DNTs and differed only in their presentation related to their location. The novel aspects of this report are the radiologic resemblance of DNT to colloid cyst and focal subependymoma-like pattern on histology. Importantly, intra-/periventricular region appears to be the most common extracortical location of cerebral DNT with a 100% disease-free survival reported in the literature.

A cortical dysembryoplastic neuroepithelial tumor initially occurring in the periventricular white matter

In this report, a rare case of dysembryoplastic neuroepithelial tumor (DNET) initially presented as a small white matter lesion with calcification adjacent to the lateral ventricle and extending to the frontal cortex after 7 years. This 1-year-old boy initially suffered from partial seizures. Initial CT revealed a small, low-density area surrounding a tiny calcified mass in the deep white matter of the left frontal lobe. Seven years later, his seizures had become intractable to antiepileptic agents, and MR imaging demonstrated a relatively large mass extending from the calcified lesion up to the adjacent cortical surface. He underwent surgery and the tumor was subtotally removed. Histological examination of the tumor verified it as a DNET consisting of clusters of small oligodendrocytes with floating neurons in the mucoid background. The pattern of the tumor progression in this case suggests that a DNET in the cortex originates from the subependymal germinal layer near the ventricle.

Dysembryoplastic neuroepithelial tumor located in pericallosal and intraventricular area in a child. Case report

Dysembryoplastic neuroepithelial tumors (DNETs) are frequently seen in children and young adults with intractable epilepsy, and are typically located in the temporal cortex. Extracortical location of DNET is a very rare occurrence. The authors report on a child with a unique extracortical location of DNET with an extensive involvement to the supracallosal cistern and callosum, septum pellucidum, and lateral ventricle ependyma. The authors discuss the radiological and pathological characteristics of the lesion and reiterate the difficulty in differentiating the histological characteristics of central neurocytoma and DNET in extracortical locations and its significance for further management planning.