Occurrence and distribution of pilomyxoid astrocytoma

Spectrum of qualitative and quantitative imaging of pilomyxoid, intermediate pilomyxoid and pilocytic astrocytomas in relation to their genetic alterations

PURPOSE

Pilomyxoid astrocytomas (PMA) are pediatric brain tumors predominantly located in the suprasellar region, third ventricle and posterior fossa, which are considered to be more clinically aggressive than pilocytic astrocytomas (PA). Another entity, intermediate pilomyxoid tumors (IPT), exists within the spectrum of pilocytic/pilomyxoid astrocytomas. The 2021 WHO CNS classification refrained from assigning grade 1 or 2 status to PMA, thereby reflecting the need to further elucidate their clinical and imaging characteristics.

METHODS

We included a total of 15 patients with PMA, IPT and suprasellar PA. We retrospectively evaluated immunohistochemistry, imaging findings and diffusion characteristics within these tumors as well as whole exome sequencing for three of the cases.

RESULTS

87% of the tumors were supratentorial with 11 cases suprasellar in location, 1 case located in the frontal white matter and 1 in the hippocampus. 6 cases demonstrated intraventricular extension. ADC values were higher in PMA and IPT than PA. 3 cases demonstrated KIAA1549-BRAF-fusion, 2 had BRAF[Formula: see text]-mutation and 6 were BRAF-wildtype. All cases had recurrence/progression on follow-up.

CONCLUSION

PMA and IPT do not demonstrate aggressive imaging characteristics in respect to their diffusion imaging with ADC values being higher than PA. Lack of BRAF-alteration in PMA corresponded to atypical location of tumors with atypical driver mutations and mechanisms.

Failure to Thrive Revealing a Pilomyxoid Astrocytoma: An Uncommon Case Report with Literature Review

Pilomyxoid astrocytoma (PMA) is a freshly described figure of low-grade neoplasms encountered in early childhood. Nevertheless, its precise classification by the World Health Organization (WHO) is still debatable. Making an exact diagnosis relies on histological and immunohistochemical pathognomonic features with specific radiological findings. PMA behaves aggressively with a shorter progression-free survival, and its management is unfortunately still arguable. We describe a rare case of PMA involving the suprasellar region who displays symptoms consistent with diencephalic syndrome. The diagnosis was made by magnetic resonance imaging (MRI) focused on the hypothalamic-pituitary axis, and the patient underwent a subtotal tumor resection combined with chemotherapy. Diagnosis of brain tumors should be kept in mind in young children with generalized and severe unexplained loss of subcutaneous fat with failure to thrive after ruling out classical causes.

Pilomyxoid astrocytoma of the thoracic spinal cord: Extremely rare case report of over 70-year-old patient

The Pilomyxoid is rare tumor in elderly population, in addition to the occurrence of an isolated lesion in spinal cord is extremely rare in non-pediatric population. Taking biopsy and subtotal resection is the starting point in essential approach for the treatment. After defining the histopathological nature of the tumor and specified that is Pilomyxoid, the next step is the combination of reoperation and adjuvant therapy.

Midline Astrocytic Tumors in Children: A Retrospective Study of 152 Cases

The aim of this study was to analyze the various midline structures having preponderance for astrocytoma, their incidence, clinical features, operative approach, prognosis, and outcomes in children. It is a retrospective analysis of 152 cases with midline astrocytic tumors in children admitted between January 1995 and December 2012 in the Department of Neurosurgery at Sanjay Gandhi Postgraduate Institute of Medical sciences Lucknow, India. The mean age of the cases with midline astrocytic tumors was 9.29 ± 4.56 years. Majority of these tumors occurred in the age group of 6 to 10 years (n = 58, 38.16%), with male to female ratio being 1.66:1. Out of 152 cases, tumors located at midline cerebellum constituted majority of the cases (n = 38, 25%) followed by brain stem (n = 28, 18.42%), thalamic region (n = 24, 15.79%), corpus callosum (n = 18, 11.82%), pineal region (n = 12, 7.89%), optic nerve (n = 12, 7.89%), chiasmo-hypothalamic (n = 10, 6.58%), and septum pellucidum astrocytomas (n = 10, 6.58%). Majority of these tumors were of low-grade type (n = 136, 89.47%), and pilocytic astrocytomas were the commonest subtypes. Out of 152 cases, 136 (89.47%) cases had improved outcomes, 8 (5.26%) remained as they were in preoperative state, and mortality was seen in 8 (5.26%) of the cases at 3 to 77 months (mean 26.70 ± 9.70) of follow-up. Midline structures having preponderance for astrocytomas were midline cerebellum, brain stem, thalamus, corpus callosum, pineal region, optic nerve, chiasmo-hypothalamic, and septum pellucidum. Cerebellum was the commonest site. Most of these astrocytomas were of low grade with pilocytic astrocytoma being the commonest subtype. With meticulous presurgical planning, most of these tumors have good outcome with significant reduction in mortality and morbidity.

Incidence of childhood CNS tumours in Britain and variation in rates by definition of malignant behaviour: population-based study

Background

Intracranial and intraspinal tumours are the most numerous solid tumours in children. Some recently defined subtypes are relatively frequent in childhood. Many cancer registries routinely ascertain CNS tumours of all behaviours, while others only cover malignant neoplasms. Some behaviour codes have changed between revisions of the International Classification of Diseases for Oncology, including pilocytic astrocytoma, downgraded to uncertain behaviour in ICD-O-3.

Methods

We used data from the population-based National Registry of Childhood Tumours, which routinely included non-malignant CNS tumours, to document the occurrence of CNS tumours among children aged < 15 years in Great Britain during 2001–2010 and to document the descriptive epidemiology of childhood CNS tumours over the 40-year period 1971–2010, during which several new entities were accommodated in successive editions of the WHO Classification and revisions of ICD-O. Eligible cases were all those with a diagnosis included in Groups III (CNS tumours) and Xa (CNS germ-cell tumours) of the International Classification of Childhood Cancer, Third Edition. The population at risk was derived from annual mid-year estimates by sex and single year of age compiled by the Office for National Statistics and its predecessors. Incidence rates were calculated for age groups 0, 1–4, 5–9 and 10–14 years, and age-standardised rates were calculated using the weights of the world standard population.

Results

Age-standardised incidence in 2001–10 was 40.1 per million. Astrocytomas accounted for 41%, embryonal tumours for 17%, other gliomas for 10%, ependymomas for 7%, rarer subtypes for 20% and unspecified tumours for 5%. Incidence of tumours classified as malignant and non-malignant by ICD-O-3 increased by 30 and 137% respectively between 1971-75 and 2006–10.

Conclusions

Total incidence was similar to that in other large western countries. Deficits of some, predominantly low-grade, tumours or differences in their age distribution compared with the United States and Nordic countries are compatible with delayed diagnosis. Complete registration regardless of tumour behaviour is essential for assessing burden of disease and changes over time. This is particularly important for pilocytic astrocytoma, because of its recent downgrading to non-malignant and time trends in the proportion of astrocytomas with specified subtype.

Spinal Pilomyxoid Astrocytoma

Pilomyxoid astrocytoma (PMA) is a rare brain tumour generally located in the chiasmatic-hypothalamic region. In comparison to pilocytic astrocytoma, PMA has distinct histopathological features, aggressive clinical behaviour, a high recurrence rate, and early cerebrospinal fluid dissemination. Only 14 cases of PMA have been reported in the spinal cord since its pathological description in 1999. Here, we report the 15th case in a 3-year-old girl who was treated with chemoradiotherapy and followed up for 5 years. In this report, we also present a review of spinal PMA including treatment options and prognosis.

Recent Progress in the Pathology and Genetics of Pilocytic and Pilomyxoid Astrocytomas

Pilocytic and pilomyxoid astrocytomas are some of the most common gliomas in children and young adults. These gliomas are indolent neoplasms with long overall survival probability. The genetic characteristics of these neoplasms are well known, and our deepened understanding of their associated molecular alterations has led to the development of novel treatment strategies and approaches. Currently, we can account for some of the unusual behavior, such as oncogene-induced senescence, associated spontaneous regression, anaplastic transformation, and cerebrospinal dissemination, of these gliomas. Nevertheless, enigmatic issues continue to surround these chronic tumors. Here, we review the classical and uncommon clinical pathological and genetic features of these indolent gliomas.

Fluorescence guided resection with 5-aminolevulinic acid of a pilomyxoid astrocytoma of the third ventricle

Fluorescence-guided resection with 5-aminolevulinic acid has been shown to be useful in the resection of certain brain tumors other than high grade gliomas, facilitating the intraoperative differentiation of neoplastic tissue. The technique enables the surgeon to ensure that no tumor fragments remain, thereby achieving higher rates of complete resection. Tihan first described pilomyxoid astrocytomas in 1999. They are currently classified as grade II astrocytoma according to the WHO classification system and, because of their tendency to recur and their dissemination through the cerebrospinal fluid pathways, they are considered to be more aggressive than pilocytic astrocytoma. As a result, management of these tumors must be more aggressive, always aiming for complete macroscopic resection whenever possible. In this article, we present a case of pilomyxoid astrocytoma of the third ventricle in which the use of fluorescence-guided resection with 5-ALA facilitated complete resection. Imaging tests performed after five years revealed no signs of recurrence and no adjuvant radiotherapy or chemotherapy was required. This article also comprises a review of the literature concerning the characteristics and management of this tumor, which was recently considered to be a different histopathological entity.

Unresolved drooling in a previously healthy child caused by a brainstem malignancy

Drooling occurs commonly in children below the age of two. In a small group of children this persists and an otorhinolaryngology consultation is sought. In children with no neurological abnormality or comorbidity, reassurance and behavioural management is often suggested. We present a case where drooling was the presenting feature of brain stem malignancy. Diagnosis was suggested following a sleep study demonstrating central apnoeas. Magnetic resonance imaging (MRI) showed an intra-axial brainstem tumour. This case highlights the importance of multidisciplinary team (MDT) management of children with persistent drooling of unknown cause.

Single-Agent Carboplatin for a Rare Case of Pilomyxoid Astrocytoma of the Spinal Cord in an Adult with Neurofibromatosis Type 1

INTRODUCTION

Pilomyxoid astrocytoma (PMA) is a rare and more aggressive variant of pilocytic astrocytoma, which usually affects young children and is most often located in the hypothalamic/chiasmatic region. The association of PMA with underlying genetic disorders is not well known.

METHODS

We identified a 23-year-old woman with a PMA of the spinal cord who was simultaneously diagnosed with neurofibromatosis type 1. Diagnosis of neurofibromatosis type 1 was made clinically and confirmed with genetic testing that revealed a heterozygous one-amino-acid deletion (c.2970-2972 delAAT) in exon 17 of the NF1 gene, which is correlated with a milder phenotype. The patient underwent a partial surgical resection of the spinal cord tumor followed by adjuvant carboplatin 560 mg/m2 every 4 weeks. Radiation was avoided due to risks associated with neurofibromatosis type 1.

RESULTS

At the 11-month follow-up, the patient maintained a partial radiographic response as well as complete resolution of her neurologic deficits.

CONCLUSION

To our knowledge, this is the first reported case of an adult patient with neurofibromatosis type 1 and a spinal cord PMA. Single-agent carboplatin was effective and well-tolerated.

Pilomyxoid astrocytoma in the adult cerebellum

Pilomyxoid astrocytoma (PMA) is a recently recognised World Health Organization (WHO) Grade II tumour that was previously characterised as a subtype of the WHO Grade I pilocytic astrocytoma (PA). PMA has a histological appearance distinct from PA and a poorer prognosis due to its greater propensity for local recurrence and cerebrospinal dissemination. Although originally considered a paediatric tumour involving mainly the hypothalamic and chiasmatic region, reports of the lesion occurring in the adult population and other areas of the neuroaxis are emerging. We review the literature on PMA within the adult population and present the first case of PMA in the cerebellum of an adult female.

Differential imaging characteristics and dissemination potential of pilomyxoid astrocytomas versus pilocytic astrocytomas

INTRODUCTION

Pilomyxoid astrocytoma (PMA) is a rare WHO grade II tumor occurring most often in young children. PMA is associated with worse outcome as compared to the pathologically related pilocytic astrocytoma (PA). The radiological differentiation of PMAs from PAs is challenging. Furthermore, it is not completely clarified whether PMA is associated with a higher rate of cerebrospinal fluid (CSF) dissemination in the youngest pediatric population as compared to PA. The aim of our study was firstly to compare imaging features of these tumors and, secondly, to evaluate the occurrence of CSF dissemination.

METHODS

The study population included 15 children with PMA and 32 children with PA. The initial MRI and CT scans from the time of the diagnosis were retrospectively analyzed according to standardized criteria and the findings compared between the two tumor types. Furthermore, we also compared the occurrence of imaging evidences of CSF dissemination.

RESULTS

PMAs showed less frequently cystic components (p = 0.03) and never had large tumor cysts. Gadolinium enhancement of PMAs was more frequently homogeneous (p = 0.006). PMAs appeared to show more often intratumoral hemorrhages (p = 0.047). Within the subgroup of children <6 years of age, the PMA histology tended to have a larger effect on the occurrence of CSF dissemination than the age (p = 0.05 vs. 0.12).

CONCLUSION

Some imaging features like enhancement pattern or presence of cysts or hemorrhage may help differentiating these low-grade gliomas. Our results confirm previous scarce data suggesting a higher rate of CSF dissemination in PMAs, even in the youngest patient population.

Pilomyxoid Astrocytoma (PMA) Shows Significant Differences in Gene Expression vs. Pilocytic Astrocytoma (PA) and Variable Tendency Toward Maturation to PA

Pilomyxoid astrocytomas (PMAs) manifest a more aggressive clinical course than pilocytic astrocytomas (PAs). Development of effective therapies demands a better biological understanding of PMA. We first conducted gene expression microarray analysis of 9 PMA and 13 PA from infra- and supratentorial sites. Unsupervised hierarchical clustering analysis demonstrated that tumors are grouped according to anatomic site, not diagnosis. Gene expression profiles were then contrasted between eight PMAs and six PAs, all supratentorial/hypothalamic/chiasmal. Clinical outcome of PMAs varied, with four out of four patients with diencephalic syndrome succumbing to disease, one of whom showed bulky metastatic leptomeningeal spread at autopsy, with bimodal maturation to PA in some areas and de-differentiation to glioblastoma in others. A surviving child has undergone multiple surgical debulking, with progressive maturation to PA over time. Ontology-enrichment analysis identified overexpression in PMAs of extracellular matrix and mitosis-related genes. Genes overexpressed in PMA vs. PA, ranked according to fold-change, included developmental genes H19, DACT2, extracellular matrix collagens (COL2A1; COL1A1) and IGF2BP3 (IMP3), the latter previously identified as an adverse prognostic factor in PMA and PA.