Tumor characteristics and surgical outcomes of intracranial subependymomas: a systematic review and meta-analysis

Ependymal Tumors: Overview of the Recent World Health Organization Histopathologic and Genetic Updates with an Imaging Characteristic

The 2021 World Health Organization Classification of Tumors of the Central Nervous System (CNS5), introduced significant changes, impacting tumors ranging from glial to ependymal neoplasms. Ependymal tumors were previously classified and graded based on histopathology, which had limited clinical and prognostic utility. The updated CNS5 classification now divides ependymomas into 10 subgroups based on anatomic location (supratentorial, posterior fossa, and spinal compartment) and genomic markers. Supratentorial tumors are defined by zinc finger translocation associated (ZFTA) (formerly v-rel avian reticuloendotheliosis viral oncogene [RELA]), or yes-associated protein 1 (YAP1) fusion; posterior fossa tumors are classified into groups A (PFA) and B (PFB), spinal ependymomas are defined by MYCN amplification. Subependymomas are present across all these anatomic compartments. The new classification kept an open category of "not elsewhere classified" or "not otherwise specified" if no pathogenic gene fusion is identified or if the molecular diagnosis is not feasible. Although there is significant overlap in the imaging findings of these tumors, a neuroradiologist needs to be familiar with updated CNS5 classification to understand tumor behavior, for example, the higher tendency for tumor recurrence along the dural flap for ZFTA fusion-positive ependymomas. On imaging, supratentorial ZFTA-fused ependymomas are preferentially located in the cerebral cortex, carrying predominant cystic components. YAP1-MAMLD1-fused ependymomas are intra- or periventricular with prominent multinodular solid components and have significantly better prognosis than ZFTA-fused counterparts. PFA ependymomas are aggressive paramedian masses with frequent calcification, seen in young children, originating from the lateral part of the fourth ventricular roof. PFB ependymomas are usually midline, noncalcified solid-cystic masses seen in adolescents and young adults arising from the fourth ventricular floor. PFA has a poorer prognosis, higher recurrence, and higher metastatic rate than PFB. Myxopapillary spinal ependymomas are now considered grade II due to high recurrence rates. Spinal-MYCN ependymomas are aggressive tumors with frequent leptomeningeal spread, relapse, and poor prognosis. Subependymomas are noninvasive, intraventricular, slow-growing benign tumors with an excellent prognosis. Currently, the molecular classification does not enhance the clinicopathologic understanding of subependymoma and myxopapillary categories. However, given the molecular advancements, this will likely change in the future. This review provides an updated molecular classification of ependymoma, discusses the individual imaging characteristics, and briefly outlines the latest targeted molecular therapies.

Supratentorial and Infratentorial Ependymoma

Ependymomas are the third most common intracranial tumor in children, presenting in both the supratentorial and infratentorial compartments. They may present in infants, young children, and adolescents with symptoms depending on size, location, and the age of the patient. The ideal imaging for evaluation and treatment is MRI. This is crucial for preoperative evaluation and planning, as well as postoperative assessment and evaluating the efficacy of treatment. Essentially without exception, aggressive surgery aimed at complete resection is the initial and most important factor in the long-term outcome of all these children. Histopathologic diagnosis for intracranial pediatric ependymoma has been narrowed to grade II and grade III, no longer characterized as classic and anaplastic. Subsequent conformal photon or proton beam irradiation is an established post-surgical therapy, with solid evidence that it benefits survival and offers lower toxicity to the normal brain of the young child. Although chemotherapeutic treatment has not been generally impactful, immunotherapeutic interventions may be on the horizon. Updated molecular subgrouping of ependymoma is changing the post-resection approach of these tumors with regard to both treatment and outcome. Excluding spinal ependymoma and subependymoma, there are four subtypes that are defined by genetic characteristics, two found in the supratentorial compartment, ST-EPN-YAP1 and ST-EPN-ZFTA, and two in the posterior fossa, PF-EPN-A and PF-EPN-B. Younger children harboring ZFTA fusion-positive supratentorial and type A posterior fossa tumors, regardless of histology, tend toward the poorest outcomes. On the contrary, older children with supratentorial YAP1 fusion-positive ependymomas and type B posterior fossa tumors may survive with surgery alone. The paradigm shift regarding the behavior of the various childhood ependymoma subtypes will hopefully lead to targeted, individualized therapies and improved outcomes.

Staged or simultaneous operations for ventriculoperitoneal shunt and cranioplasty: Evidence from a meta-analysis

OBJECTIVE

To date, there is no consensus on the surgery strategies of cranioplasty (CP) and ventriculoperitoneal shunt (VPS) placement. This meta-analysis aimed to investigate the safety of staged and simultaneous operation in patients with comorbid cranial defects with hydrocephalus to inform future surgery protocols.

METHODS

A meta-analysis of PubMed, Ovid, Web of Science, and Cochrane Library databases from the inception dates to February 8, 2023 adherent to PRISMA guidelines was conducted. The pooled analyses were conducted using RevMan 5.3 software. The outcomes included postoperative infection, reoperation, shunt obstruction, hematoma, and subdural effusion.

RESULTS

Of the 956 studies initially retrieved, 10 articles encompassing 515 patients were included. Among the total patients, 193 (37.48%) and 322 (62.52%), respectively, underwent simultaneous and staged surgeries. The finding of pooled analysis indicated that staged surgery was associated with lower rate of subdural effusion (14% in the simultaneous groups vs. 5.4% in the staged groups; OR = 2.39, 95% CI: 1.04-5.49, p = 0.04). However, there were no significant differences in overall infection (OR = 1.92, 95% CI: 0.74-4.97, p = 0.18), central nervous system infection (OR = 1.50, 95% CI: 0.68-3.31, p = 0.31), cranioplasty infection (OR = 1.58, 95% CI: 0.50-5.00, p = 0.44), shunt infection (OR = 1.30, 95% CI: 0.38-4.52, p = 0.67), reoperation (OR = 1.51, 95% CI: 0.38-6.00, p = 0.55), shunt obstruction (OR = 0.73, 95% CI: 0.25-2.16, p = 0.57), epidural hematoma (OR = 2.20, 95% CI: 0.62-7.86, p = 0.22), subdural hematoma (OR = 1.20, 95% CI: 0.10-14.19, p = 0.88), and intracranial hematoma (OR = 1.31, 95% CI: 0.42-4.07, p = 0.64). Moreover, subgroup analysis failed to yield new insights.

CONCLUSIONS

Staged surgery is associated with a lower rate of postoperative subdural effusion. However, from the evidence of sensitivity analysis, this result is not stable. Therefore, our conclusion should be viewed with caution, and neurosurgeons in practice should make individualized decisions based on each patient's condition and cerebrospinal fluid tap test.

Molecular Classification and Therapeutic Targets in Ependymoma

Ependymoma is a biologically diverse tumor wherein molecular classification has superseded traditional histological grading based on its superior ability to characterize behavior, prognosis, and possible targeted therapies. The current, updated molecular classification of ependymoma consists of ten distinct subgroups spread evenly among the spinal, infratentorial, and supratentorial compartments, each with its own distinct clinical and molecular characteristics. In this review, the history, histopathology, standard of care, prognosis, oncogenic drivers, and hypothesized molecular targets for all subgroups of ependymoma are explored. This review emphasizes that despite the varied behavior of the ependymoma subgroups, it remains clear that research must be performed to further elucidate molecular targets for these tumors. Although not all ependymoma subgroups are oncologically aggressive, development of targeted therapies is essential, particularly for cases where surgical resection is not an option without causing significant morbidity. The development of molecular therapies must rely on building upon our current understanding of ependymoma oncogenesis, as well as cultivating transfer of knowledge based on malignancies with similar genomic alterations.

Molecular Stratification of Childhood Ependymomas as a Basis for Personalized Diagnostics and Treatment

Ependymomas are among the most enigmatic tumors of the central nervous system, posing enormous challenges for pathologists and clinicians. Despite the efforts made, the treatment options are still limited to surgical resection and radiation therapy, while none of conventional chemotherapies is beneficial. While being histologically similar, ependymomas show considerable clinical and molecular diversity. Their histopathological evaluation alone is not sufficient for reliable diagnostics, prognosis, and choice of treatment strategy. The importance of integrated diagnosis for ependymomas is underscored in the recommendations of Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy. These updated recommendations were adopted and implemented by WHO experts. This minireview highlights recent advances in comprehensive molecular-genetic characterization of ependymomas. Strong emphasis is made on the use of molecular approaches for verification and specification of histological diagnoses, as well as identification of prognostic markers for ependymomas in children.