Malignant transformation in pediatric spinal intramedullary tumors: case-based update

BACKGROUND: In children, intramedullary spinal cord neoplasms are rare. These are typically low-grade neuroepithelial tumors, most commonly astrocytomas, ependymomas, and gangliogliomas. Malignant transformation, while common in recurrent adult low-grade gliomas, is an unusual event in pediatric low-grade neoplasms, specifically in intramedullary spinal cord tumors. ILLUSTRATIVE CASES: We report two cases of malignant transformation in low-grade neuroepithelial tumors of the pediatric intramedullary spinal cord. Two children with intramedullary tumors, one with a WHO grade I ganglioglioma and one with a low-grade astrocytoma, were treated surgically, diagnosed histologically, and followed through the course of their disease. Both patients' tumors transformed to higher grades without prior irradiation or chemotherapy, and without a genetic predisposition to tumorigenesis. DISCUSSION: Malignant transformation can occur in low-grade intramedullary neoplasms in children. This is a novel documented event for pediatric intramedullary spinal cord tumors and a rare event for all pediatric low-grade neuroepithelial tumors without induction by irradiation. A survey of the relevant literature reveals an underwhelming number of studies focusing on malignant transformation in children's CNS tumors relative to adults. Further investigation into molecular mechanisms of pediatric low-grade neoplasms may reveal more aggressive tumor sub-variants predisposed to malignant degeneration.     

Neuropathological and molecular aspects of low-grade and high-grade gliomas

Gliomas are the most frequent primary brain tumors. They are derived from glial cells of astrocytic, oligodendroglial and ependymal origin. According to the WHO classification of brain tumors gliomas are divided in low-grade (grades I and II) and high-grade (grades III and IV) tumors. Low-grade tumors are well-differentiated, slow-growing lesions. Grade I tumors are well-circumscribed and often surgically curable, whereas grade II tumors are diffuse, infiltrating lesions with a marked potential over time for progression towards a high-grade malignant tumor. The optimal management of low-grade gliomas is still debated. Important prognostic factors such as histology, grade and location of the tumor, age and functional status of the patient, must be taken into consideration to select the most appropriate treatment. Major advances in the molecular genetic assessment of brain tumors and of gliomas in particular have lead to the identification of several molecular markers playing a crucial role in the development of gliomas and in their malignant transformation. Some of those markers were found very useful to assist in the histological diagnosis and to predict survival and response to therapy. A combined deletion of chromosomes arms 1p and 19q can be found in more than 50% of Grade II and III oligodendrogliomas and has been associated with chemosensitivity and a better prognosis. Once limited to the field of research, molecular biology has now entered the daily neuropathological practice and will undoubtedly play an increasing role in future classification and treatment of brain tumors.     

Biology molecular of glioblastomas

Glioblastomas, the most frequent and malignant human brain tumors, may develop de novo (primary glioblastoma) or by progression from low-grade or anapalsic astrocytoma (secondary glioblastoma). The molecular alteration most frequent in these tumor-like types is the loss of heterozygosity on chromosome 10, in which several genes have been identified as tumors suppressor. The TP53/MDM2/P14arf and CDK4/RB1/ P16ink4 genetic pathways involved in cycle control are deregulated in the majority of gliomas as well as genes that promote the cellular division, EGFR. Finally the increase of growth and angiogenics factors is also involved in the development of glioblastomas. One of the objectives of molecular biology in tumors of glial ancestry is to try to find the genetic alterations that allow to approach better the classification of glioblastomas, its evolution prediction and treatment. The new pathmolecular classification of gliomas should improve the old one, especially being concerned about the oncogenesis and heterogeneity of these tumors. It is desirable that this classification had clinical applicability and integrates new molecular findings with some known histological features with pronostic value. In this paper we review the most frequent molecular mechanisms involved in the patogenesis of glioblastomas.     

Progress in clinical neurosciences: Advances in the management of low-grade gliomas

The management of low-grade gliomas represents one of the most challenging and controversial areas in neuro-oncology. Many aspects of the treatment of low-grade gliomas are debated, including the optimal timing of surgery and radiotherapy, the benefit of extensive surgery, and the impact of these variables on the natural history of these indolent and generally incurable tumours. The recently published results of several large multicentre trials addressing the timing and dose of radiotherapy have provided solid evidence for delayed and reduced dose irradiation. These studies have also confirmed prognostic variables that can be used to guide management of individual patients. Among these variables is the observation that tumours with oligodendroglial features have a better natural history and response profile. The recognition that as many as two thirds of low-grade gliomas have oligodendroglial features, advances in molecular diagnostics making accurate pathologic diagnosis of oligodendroglial tumours possible, and the established chemosensitivity of malignant oligodendrogliomas, have raised new issues surrounding the potential value of chemotherapy for low-grade gliomas. This review will be restricted to low-grade diffuse astrocytomas, oligodendrogliomas, and low-grade mixed oligoastrocytomas in adults, and provide evidence-based guidelines for the management of these tumours, including the emerging role of chemotherapy as initial treatment.     

State of the art chemotherapeutic management of pediatric brain tumors

CNS tumors are the most common solid tumor of childhood. This article will review current treatments for pediatric brain tumors; low-grade gliomas, high-grade gliomas, medulloblastomas and ependymomas. It will also highlight the treatments that are used for brain tumors in very young children and in children with recurrent brain tumors. The management of recurrent pediatric brain tumors unresponsive to standard therapy will be discussed. The agents used in this setting are mainly biological modifiers, which attempt to provide molecularly targeted therapy. Future directions of therapy for pediatric brain tumors are described. Future treatment paradigms will need to consider examining the use of multiple biological modifiers. Similarly, these agents will need to be examined in combination with cytotoxic chemotherapy. Finally, the future direction of pediatric neuro-oncology and the focus of the field as it battles pediatric brain tumors is discussed.     

Childhood brain tumors: epidemiology, current management and future directions

Brain tumors are the most common solid tumors in children. With the increasingly widespread availability of MRI, the incidence of childhood brain tumors seemed to rise in the 1980s, but has subsequently remained relatively stable. However, management of brain tumors in children has evolved substantially during this time, reflecting refinements in classification of tumors, delineation of risk groups within histological subsets of tumors, and incorporation of molecular techniques to further define tumor subgroups. Although considerable progress has been made in the outcomes of certain tumors, prognosis in other childhood brain tumor types is poor. Among the tumor groups with more-favorable outcomes, attention has been focused on reducing long-term morbidity without sacrificing survival rates. Studies for high-risk groups have examined the use of intensive therapy or novel, molecularly targeted approaches to improve disease control rates. In addition to reviewing the literature and providing an overview of the complexities in diagnosing childhood brain tumors, we will discuss advances in the treatment and categorization of several tumor types in which progress has been most apparent, as well as those in which improvements have been lacking. The latest insights from molecular correlative studies that hold potential for future refinements in therapy will also be discussed.     

血管内皮生长因子与水孔蛋白4在胶质瘤及脑转移瘤中的表达及意义

目的 探讨血管内皮生长因子(VEGF)与水孔蛋白4(AQP4)在胶质瘤及脑转移瘤中的表达,并探讨两者与胶质瘤及脑转移瘤的组织病理学关系及在瘤周水肿形成过程中的作用.方法 选择福建医科大学附属第一医院神经外科自1999年至2001年手术切除并经病理检查证实的胶质瘤石蜡组织标本73例和脑转移瘤组织标本15例,并另取正常脑组织标本8例作为对照,应用免疫组织化学方法检测组织标本中VEGF与AOP4的表达.结果 正常脑组织中未见VEGF表达:高级别胶质瘤与低级别胶质瘤之间、低级别胶质瘤与正常脑组织之间、脑转移瘤与正常脑组织及低级别胶质瘤之间VEGF阳性表达比较差异有统计学意义(P<0.05),而脑转移瘤与高级别胶质瘤之间VEGF阳性表达比较差异无统计学意义(P>0.05).AQP4在所有组织标本中均有表达,正常脑组织与高级别胶质瘤、脑转移瘤之间,低级别胶质瘤与高级别胶质瘤、脑转移瘤之间AQP4阳性表达比较差异有统计学意义(P<0.05),而正常脑组织与低级别胶质瘤之间、脑转移瘤与高级别胶质瘤之间AQP4阳性表达比较差异无统计学意义(P>0.05).Spearman相关分析显示两者在胶质瘤及脑转移瘤组织中表达呈正相关关系(r=0.516,P<0.05).结论 VEGF与AQP4是参与形成肿瘤周围水肿的重要分子生物学因素,且两者可能存在某种协同作用.     

An integrative molecular and genomic analysis of pediatric hemispheric low-grade gliomas: an update

Hemispheric low-grade gliomas account for the second most common location in pediatric low-grade gliomas (PLGGs) after the cerebellum. The pathological spectrum includes gangliogliomas, dysembryoplastic neuroepithelial tumors (DNETs), diffuse astrocytomas, pilocytic astrocytomas, and pleomorphic xanthoastrocytomas (PXAs), among others. Clinically, hemispheric PLGGs represent a well-recognized cause of intractable epilepsy in children and adolescents. With an excellent long-term outcome, surgery remains the cornerstone and patients with gross total resection typically do not need any further therapies. The recent literature about hemispheric PLGGs was reviewed to provide an up-to-date overview of the molecular and cell biology of these tumors. Hemispheric PLGGs can harbor multiple alterations involving BRAFV600E, FGFR, NTRK, MYB/MYBL1, IDH, and BRAF-KIAA1549 fusions. However, the clinical significance of most of these alterations is still to be defined. The role of RAS/MAPK mutations and other alterations in hemispheric PLGGs is of interest from diagnostic, prognostic, and therapeutic perspectives. Molecular testing for these tumors should be encouraged, since the findings can have an important impact not only in prognosis but also in therapeutic strategies.     

Brainstem gliomas

Introduction Brainstem gliomas have historically been one of the most difficult pediatric cancers to treat. Tumors arising in the brainstem were once uniformly discounted as surgically unresectable lesions. Early neurosurgeons thought this location to be inoperable and fraught with disaster. The advent of computed tomography (CT), magnetic resonance imaging (MRI), and sophisticated neurophysiological monitoring techniques have significantly advanced the surgical treatment of these precarious lesions.Review Brainstem gliomas are now recognized as a heterogenous group of tumors. They have been broadly classified into several categories depending upon the classification scheme. All these classification systems provide a framework to predict growth patterns, surgical resectability, and overall prognosis of these tumors. These systems allow the surgeon to obtain a better understanding of the distinction between low-grade tumors and diffuse inoperable tumor types. The authors review the current literature and management of brainstem tumors.     

Oligodendroglial tumors

Oligodendroglial tumors represent approximately 4-7% of all gliomas; however, in some series the incidence has been reported to be as high as 10-20% because of improved histological appreciation and recently recognized molecular signatures. Oligodendroglial tumors are classified as being low-grade oligodendroglial tumors, high-grade anaplastic oligodendroglial tumors or mixed oligo-astrocytic tumors. The mixed tumors can again be low-grade or high-grade. The recent European Organization for Research and Treatment of Cancer and Radiation Therapy Oncology Group randomized trials have provided level 1 evidence regarding the best management of these tumors. This review provides an overview of oligodendroglial tumors and discusses contemporary and evolving treatment strategies.     

PET and SPECT studies in children with hemispheric low-grade gliomas

Molecular imaging is playing an increasing role in the pretreatment evaluation of low-grade gliomas. While glucose positron emission tomography (PET) can be helpful to differentiate low-grade from high-grade tumors, PET imaging with amino acid radiotracers has several advantages, such as better differentiation between tumors and non-tumorous lesions, optimized biopsy targeting, and improved detection of tumor recurrence. This review provides a brief overview of single-photon emission computed tomography (SPECT) studies followed by a more detailed review of the clinical applications of glucose and amino acid PET imaging in low-grade hemispheric gliomas. We discuss key differences in the performance of the most commonly utilized PET radiotracers and highlight the advantage of PET/MRI fusion to obtain optimal information about tumor extent, heterogeneity, and metabolism. Recent data also suggest that simultaneous acquisition of PET/MR images and the combination of advanced MRI techniques with quantitative PET can further improve the pretreatment and post-treatment evaluation of pediatric brain tumors.     

Management of patients with low-grade gliomas

The accurate diagnosis and management of patients who have infiltrating low-grade gliomas is increasing in importance. Recent advances in molecular characterization, imaging, and treatment of these tumors underscore this current focus of investigations.     

Expression of connexin 43 and connexin 32 gap-junction proteins in epilepsy-associated brain tumors and in the perilesional epileptic cortex

The expression of the gap-junction proteins connexin (CX) 43 and 32 was evaluated in surgical specimens of brain tumors and perilesional cortex from patients with chronic medically intractable epilepsy. In human normal brain CX32 was expressed in neurons and oligodendrocytes. CX32 immunoreactivity (IR) was observed in the neuronal component of glioneuronal tumors and in all oligodendrogliomas, 50% of which showed strong labeling, independent of the grade of differentiation. CX43, normally expressed in astrocytes, was also detected in most of the human astrocytomas and in the astroglial component of glioneuronal tumors. Whereas most of the low-grade gliomas (>60%) showed strong membranous staining, most high-grade astrocytomas exhibited a reduction of the typical plasma membrane CX43-IR and intracytoplasmic localization. Immunoblot analysis showed different CX43 isoforms in control cortex and in low-grade gliomas. However, only one single isoform (corresponding to the non-phosphorylated form of CX43) appeared to be present in most high-grade gliomas. Increased expression of CX43 protein was present in reactive astrocytes in the epileptic cortex surrounding low-grade tumors as compared to control cortex, indicating the existence of a regulatory pathway involving CX43 in the reorganization of the astrocytic syncytium in regions undergoing reactive gliosis. The high expression of connexin proteins in low-grade tumors and in the peritumoral reactive astrocytes suggests that they could contribute to tumor-related seizures.     

脑胶质瘤端粒酶的活性研究

目的 探讨各类脑胶质瘤端粒酶的活性和端粒酶在胶质瘤的恶性程度评估、预后预测等方面的意义。方法 利用TRAP－ELISA方法检测27例胶质瘤中端粒酶的活性，结合肿瘤的病理分类资料进行对照分析。结果 27例胶质瘤中，低级别胶质瘤（星形细胞瘤Ⅰ－Ⅱ级、少胶质细胞瘤和室管膜瘤）14例，端粒酶阳性2例(16．7%)；高级别胶质瘤（呈形细胞瘤Ⅲ－Ⅳ级和间变性室管膜瘤）13例，端粒酶阳性10例（76．9％）。两组之间端粒酶阳性率有显著差异（P＜0．01）。另外，两组之间端粒酶活性定量水平也有显著差异（P＜0．05）。端粒酶阳性组和端粒酶阴性组胶质瘤患者在性别、年龄方面无显著差异（P＞0．05）。10例正常脑组织中未检测到端粒酶活性。结论 端粒酶活性的激活在胶质瘤中是常见的现象。不同恶性程度的胶质瘤，端粒酶活性的阳性率和端粒酶活性水平定量差异显著。端粒酶作为肿瘤标志物，在胶质瘤的恶性程度评估1预后预测等方面具有重要的意义。     

Brain tumors in children

Childhood brain tumors are the leading cause of cancer-related morbidity and mortality in the pediatric years and differ from primary central nervous system tumors occurring in adults. Management strategies must take into account not only the tumor type, but the age of the patient and the likelihood of treatment-induced nervous system damage. With current means of treatment, most children older than 3 years can be effectively treated. Chemotherapy has taken on an increasing role in the treatment of childhood medulloblastomas, low-grade gliomas, and high-grade gliomas. Some tumor types, especially atypical teratoid tumors, brainstem gliomas, malignant gliomas, and malignant infantile tumors, remain significant therapeutic dilemmas.     

Characterisation of molecular alterations in microdissected archival gliomas

Classification of gliomas according to their molecular characteristics may be important in future histopathological diagnosis. However, gliomas frequently display heterogeneity at the histological, biological and molecular level. In this study of archival diagnostic gliomas, precision microdissection was used to enrich samples in the most malignant cells or to investigate intratumoural histological heterogeneity. Analysis of tumour samples microdissected from the most aggressive regions, representative of the histopathological diagnosis, revealed PTEN mutations in 4/14 anaplastic astrocytomas, 4/13 glioblastomas and 1 gliosarcoma, but not in 19 low-grade gliomas. Using a novel PCR procedure and direct sequence analysis of the entire coding sequence, TP53 mutations were detected in 1/3 pilocytic astrocytomas, 3/13 astrocytomas, 4/14 anaplastic astrocytomas, 5/13 glioblastomas and 1 gliosarcoma. All but one of the tumours with TP53 mutation showed p53 immunopositivity, but 5 low-grade and 10 high-grade gliomas had p53 protein nuclear accumulation in the absence of detectable mutation. p53 status was unrelated to p21 expression. Neither PTEN nor TP53 mutations influenced the proliferative index or microvessel density of high-grade astrocytomas. Unusual findings include: TP53 mutation in a juvenile pilocytic astrocytoma; TP53 and PTEN mutations in a de novo glioblastoma, a gliosarcoma with identical mutations in gliomatous and sarcomatous components, and an infratentorial anaplastic astrocytoma with an earlier supratentorial grade II astrocytoma bearing the same TP53 mutation but not the PTEN mutation or loss of heterozygosity (LOH) of 10q23. Similarly, the transition to high-grade histology was associated with acquisition of PTEN mutations and 10q23.3 LOH in two de novo high-grade tumours with regions of low-grade histology.     

Histopathological-molecular genetic correlations in referral pathologist-diagnosed low-grade "oligodendroglioma"

Allelic loss of chromosome 1p predicts increased chemosensitivity and better survival in oligodendroglial tumors. Clinical testing for 1p loss in oligodendroglial tumors at our hospital has allowed us to postulate that certain histological appearances are associated with 1p allelic status. Forty-four cases received for genetic testing were diagnosed by referring pathologists as pure low-grade oligodendroglioma. Central neuropathological review divided the series equally into 22 cases with classical oligodendroglioma histology and 22 with more astrocytic features. Molecular genetic analyses demonstrated 1p loss in 19 of 22 classic oligodendrogliomas (86%) and maintenance of both 1p alleles in 16 of 22 gliomas with astrocytic features (73%). No glial fibrillary acidic protein-positive cell type (gliofibrillary oligodendrocyte, minigemistocyte, cellular processes) was associated with 1p allelic status. Fourteen of the 44 cases were treated with chemotherapy at tumor progression: 3 "astrocytic" gliomas with 1p loss responded to PCV chemotherapy and 2 classic oligodendrogliomas that maintained both 1p alleles included a responder and a non-responder. These results suggest that histological appearance correctly predicts genotype in approximately 80% of low-grade gliomas, but that tumor genotype more closely predicts chemosensitivity. As a result, such objective molecular genetic analyses should be incorporated into patient management and into clinical trials of low-grade diffuse gliomas.     

Treatment of low-grade gliomas in children: an update

Pediatric low-grade gliomas are a heterogeneous group of tumors that require integration of the pathology and radiographic appearance with the biologic heterogeneity associated with these tumors. Balancing surgery, radiation and chemotherapy to optimize disease control while limiting treatment-related morbidity is of critical importance in this susceptible population and is the focus of this review.     

Leptomeningeal dissemination of low-grade gliomas in childhood

Although leptomeningeal spread (LMS) of primary CNS tumors in children has been well documented in the literature, it has rarely been reported in children with low-grade gliomas. Between 1975 and 1985, 6 of 162 children (3.7%) with low-grade gliomas treated at Children's Hospital of Philadelphia had LMS. LMS was present at diagnosis of the original tumor in one patient, was the first sign of relapse in one patient, occurred simultaneously with local relapse in two patients, and after local relapse in two patients. Pathology of the original tumor was low-grade astrocytoma in five and low-grade oligodendroglioma in one. Primary tumor site was cervical cord in three, chiasm in one, frontal lobe in one, and cerebellum in one. All of the children with LMS had undergone surgical treatment at the time of diagnosis of the primary tumor; four had total resections at some point in their course. Three of the six patients died; three are still alive after treatment with radiation therapy and/or chemotherapy. The longest survival to date has been 3 1/2 years after diagnosis of LMS. We compared clinical characteristics of these six patients with 131 children with low-grade tumors without dissemination treated at our institution during the same time period. LMS, although relatively infrequent, does occur in children with low-grade gliomas, especially spinal cord tumors. LMS may occur at any time during illness and diagnosis may be difficult unless LMS is suspected. Treatment, at times, results in clinical improvement and considerable disease control.