Tumour vasculature and angiogenic profile of paediatric pilocytic astrocytoma; is it much different from glioblastoma?

M. Sie, E. S. J. M. de Bont, F. J. G. Scherpen, E. W. Hoving and W. F. A. den Dunnen (2010) Neuropathology and Applied Neurobiology 36, 636–647
Tumour vasculature and angiogenic profile of paediatric pilocytic astrocytoma; is it much different from glioblastoma? Aims: Pilocytic astrocytomas are the most frequent brain tumours in children. Because of their high vascularity, this study aimed to obtain insights into potential angiogenic related therapeutic targets in these tumours by characterization of the vasculature and the angiogenic profile. In this study 59 paediatric pilocytic astrocytomas were compared with 62 adult glioblastomas, as a prototype of tumour angiogenesis. Methods: Microvessel density, vessel maturity in terms of basement membrane and pericyte coverage, and turnover of both endothelial and tumour cells, and vascular endothelial growth factor (VEGF) expression were evaluated in tumour tissue, immunohistochemically stained with, respectively, CD34, collagen IV, smooth muscle actin, Ki67/CD34, caspase‐3/CD34 and VEGF(‐A–D). As an indicator for vessel stability the angiopoietin (ANGPT)‐1/ANGPT‐2 balance was calculated using Real Time RT‐PCR. Results: Pilocytic astrocytoma and glioblastoma showed similar fractions of vessels covered with basement membrane and pericytes. Overlapping ANGPT‐1/ANGPT‐2 balance and VEGF‐A expression were found. Pilocytic astrocytoma had fewer but wider vessels compared with glioblastoma. Turnover of endothelial and tumour cells were relatively lower in pilocytic astrocytoma. Within pilocytic astrocytoma, higher ANGPT‐1/ANGPT‐2 balance was correlated with fewer apoptotic endothelial cells. Lower numbers of vessels were correlated with higher VEGF‐A expression. Conclusions: Despite the fact that pilocytic astrocytoma showed a different vessel architecture compared with glioblastoma, a critical overlap in vessel immaturity/instability and the angiogenic profile was seen between both tumours. These findings suggest encouraging possibilities for targeting angiogenesis (for instance with anti‐VEGF) as a therapeutic strategy in pilocytic astrocytoma.     

J1‐31 protein expression in astrocytes and astrocytomas

J1‐31 is one of the astrocytic proteins, the expression of which has not been evaluated in astrocytomas. In the present study, we studied the expression of J1‐31 protein in astrocytes and astrocytomas in comparison with GFAP, p53 and Ki‐67. Materials consisted of formalin‐fixed paraffin‐embedded tissue specimens that included five cases of normal brain, 17 of gliosis, 15 of pilocytic astrocytoma (WHO grade I), 26 of low‐grade diffuse astrocytoma (WHO grade II), four of anaplastic astrocytoma (WHO grade III), and eight of glioblastoma (WHO grade IV). GFAP was highly expressed in all specimens examined. The anti‐J1‐31 antibody exhibited strong cytoplasmic staining of reactive gliosis in 17/17 (100%) cases with a higher intensity of staining than that observed in the adjacent normal astrocytes. The antibody showed reactivity with tumor cells in 12/15 (80%) cases of pilocytic astrocytoma, although intensity of staining was generally weaker and more focal than observed in reactive gliosis. J1‐31‐positive tumor cells were detected in only 9/26 (35%) cases of the low‐grade diffuse astrocytoma and none of the cases of anaplastic astrocytoma and glioblastoma. Increasing Ki‐67 indices paralleled advancing tumor grades. p53 protein was expressed more commonly in infiltrating astrocytomas compared to pilocytic astrocytoma. In conclusion, down‐regulation of J1‐31 expression correlates with advancing grade of astrocytomas. The result suggests this protein plays some role in astrocytes that is progressively lost in malignant progression. The anti‐J1‐31 antibody may help further our understanding of astrocytes in disease and may be useful as an aid in the pathologic diagnosis of astrocytic lesions.     

Primary anaplastic pilocytic astrocytoma

We report two adult patients with pilocytic astrocytomas with anaplastic features at initial diagnosis. Pilocytic astrocytomas are low-grade astrocytomas that occur rarely in adults. Initial presentation of a pilocytic astrocytoma with anaplastic features is particularly uncommon and making a definitive diagnosis of pilocytic astrocytoma with anaplastic features can be challenging. It is critical to differentiate glioblastoma (World Health Organization [WHO] grade 4) and pilocytic astrocytoma with anaplastic features (WHO grade 3) from pilocytic astrocytoma (WHO grade 1) as there are significant therapeutic and prognostic implications. Improved therapeutic strategies are required for pilocytic astrocytomas with anaplastic features.     

An elderly case of malignant small cell glioma with hemorrhage coexistent with a calcified pilocytic astrocytoma component in the cerebellar hemisphere

Pilocytic astrocytoma is a less aggressive form of glial tumor that commonly occurs in the pediatric population, and its malignant transformation is extremely rare. Here, we report an elderly case of malignant small cell glioma with hemorrhage coexistent with a calcified pilocytic astrocytoma component. An 80‐year‐old male was found to have a right cerebellar non‐enhanced tumor with hematoma adjoining a calcified nodule. The lesion was surgically removed, and a histological examination verified that the tumor was a malignant small cell glioma with hemorrhagic change and the calcified nodule showed features of pilocytic astrocytoma. Genetic analyses revealed no glioma‐relevant genetic alterations such as IDH and BRAF mutations. Although calcification is generally observed in slowly growing gliomas, the aggressive clinical course of calcified cerebellar pilocytic astrocytoma has been previously reported. Our extremely rare case shows that careful follow‐up is necessary even for calcified pilocytic astrocytomas.     

A peculiar histopathological form of dysembryoplastic neuroepithelial tumor with separated pilocytic astrocytoma and rosette‐forming glioneuronal tumor components

Dysembryoplastic neuroepithelial tumors (DNTs) mostly display typical clinical, neuroimaging and histopathological features, but sometimes they reveal heterogeneous or non‐specific morphology, which results in diagnostic dilemmas. We present a case of a young adult with longstanding, intractable epilepsy associated with a multinodular cystic lesion in the temporal lobe. The lesion consisted of morphologically different components. In particular, a few cortical nodules displayed a specific glioneuronal element with floating neurons typically found in DNT. Two large, well‐circumscribed nodules were entirely composed of biphasic, piloid, astroglial patterns that corresponded strictly to a pilocytic astrocytoma. The well‐defined areas, which contained numerous distinct neurocytic‐like rosettes, were identical with rosette‐forming glioneuronal tumors (RGNTs). This type of neurocytic rosette was widespread within the surrounding piloid background. Some solid nodules exhibited increased cellularity, oligodendroglioma‐like elements and a focal ribbon cell arrangement. The lesion was associated with advanced reactive gliosis and foci of dysplastic changes in the adjacent cortex. The clinico‐radiological and main histopathological features were consistent with a diagnosis of a complex variant of DNT composed of pilocytic and rosette‐forming glioneuronal components. Although both piloid tissue and rosette‐like formations have been occasionally mentioned in DNT lesions, the present case of DNT was unique in its well‐circumscribed, separate pilocytic and RGNT nodules. We concluded that it represented an unusual, mixed pilocytic/RGNT variant of DNT.     

Congenital anaplastic astrocytoma differentiated into pilocytic astrocytoma: An autopsy case

We report an autopsy case of congenital astrocytoma and its histopathological changes during 5 years of the patient's development from birth to death. At birth, a right exophthalmic tumor was observed, and MRI revealed that the tumor occupied the right orbital space and had also affected the suprasellar diencephalic structures. The right orbital tumor, which was enucleated at 2 months of age, was a highly cellular tumor with moderate pleomorphism resembling anaplastic astrocytoma. On the other hand, at autopsy, a brain tumor was found in the right diencephalic region with features of pilocytic astrocytoma, accompanied by leptomeningeal dissemination. A biopsy specimen, which was obtained from the chiasmatic part of the tumor at 4 months of age, showed an intermediate appearance between the orbital tumor and the brain tumor obtained at autopsy. Immunohistochemical examination confirmed that all three phases of the tumors showed an astrocytic lineage, and the Ki‐67 labeling index decreased rapidly after 2 months of age. We believe that this congenital anaplastic astrocytoma differentiated into a pilocytic astrocytoma during the 5 years of the patient's development. The transformation of the congenital astrocytoma from anaplastic to pilocytic forms can be attributed to the nature of the tumor, namely postmitotic neoplastic cells are characterized by their ability to undergo self‐differentiation, along with the organotropism of the developing brain.     

Pilocytic astrocytoma of neurohypophysis

A case of pilocytic astrocytoma of neurohypophysis is presented. The clinical, pathological and MRI features of a rare tumor of the neurohypophysis are described. A 5‐year‐old girl presented with a 3 month history of lethargy, im‐balance and visual disturbances. A MRI revealed a large suprasellar mass. Histopathological examination demonstrated a pilocytic astrocytoma. Its astrocytic nature was confirmed by positive immunostaining for GFAP and the findings of an electron microscopy.     

Vascular endothelial growth factor receptor 2 (VEGFR-2) signalling activity in paediatric pilocytic astrocytoma is restricted to tumour endothelial cells

A. H. Sikkema, E. S. J. M. de Bont, G. Molema, A. Dimberg, P. J. Zwiers, S. H. Diks, E. W. Hoving, W. A. Kamps, M. P. Peppelenbosch and W. F. A. den Dunnen (2011) Neuropathology and Applied Neurobiology 37, 538–548 Vascular endothelial growth factor receptor 2 (VEGFR‐2) signalling activity in paediatric pilocytic astrocytoma is restricted to tumour endothelial cells Aims: Tumours depend on angiogenesis for enhanced tumour cell survival and progression. Vascular endothelial growth factor receptor (VEGFR) signalling plays a major part in this process. Previously, we evaluated tyrosine kinase activity in paediatric brain tumour tissue lysates using a peptide microarray containing 144 different tyrosine kinase peptide substrates. When applied to paediatric pilocytic astrocytoma tissue, this analysis revealed extensive phosphorylation of VEGFR‐derived peptides. The aim of the current study was to validate this result and determine the presence of VEGFR‐2 activity in paediatric pilocytic astrocytoma as the main VEGFR in terms of mitogenic signalling. In addition, the localization of VEGFR1–3 mRNA expression was assessed. Methods: VEGFR‐2 phosphorylation was determined by adopting a proximity ligation assay approach. Enrichment of endothelial markers and VEGFRs in tumour endothelium was determined by quantitative polymerase chain reaction (qPCR) analysis of laser‐microdissected blood vessels. Results: Proximity ligation assays on tumour cryosections showed the presence of phosphorylation of VEGFR‐2, which primarily localized to vascular endothelium. qPCR analysis of endothelial markers and VEGFRs showed a 13.6‐fold average enrichment of VEGFR‐2 expression in the laser‐microdissected endothelium compared to whole tumour. Also the expression of VEGFR‐1 and ‐3 was highly enriched in the endothelium fraction with an average fold‐enrichment of 16.5 and 50.8 respectively. Conclusions: Phosphorylated VEGFR‐2 is detected on endothelial cells in paediatric pilocytic astrocytoma. Furthermore, endothelial cells are the main source of VEGFR1–3 mRNA expression. This suggests a crucial role for VEGF/VEGFR‐induced angiogenesis in the progression and maintenance of these tumours.     

Multiple cystic brain lesions in a patient with pilocytic astrocytoma.

Pilocytic astrocytomas are usually present as solitary posterior cranial fossa tumours. An unusual case of pilocytic astrocytoma in a 3 year and 8 month old boy is presented. The patient presented over the course of 10 months with intermittent headaches, vomiting, gait ataxia and drowsiness. After extensive investigations magnetic resonance imaging (MRI) revealed widespread lesions throughout the central nervous system, including multiple cystic cerebral grey matter lesions. A brain biopsy was performed and pathological studies revealed pilocytic astrocytoma. The literature pertaining to neuraxis dissemination of pilocytic astrocytomas in the paediatric population is reviewed. There are only a very limited number of reports of pilocytic astrocytoma ca using multiple brain lesions, with no publications of multiple cystic brain lesions. We believe this to be a unique case of pilocytic astrocytoma presenting with widespread cystic lesions throughout the brain.     

Mixed glioneuronal tumor: A dysembryoplastic neuroepithelial tumor with rosette‐forming glioneuronal tumor component

Neuronal and mixed neuronal‐glial tumors of the CNS show a wide spectrum of components. Here, we report an unusual case of brain tumor with combined histological features of dysembryoplastic neuroepithelial tumor (DNT) and rosette‐forming glioneuronal tumor (RGNT) in a 23‐year‐old man. It arose in the left anterior cingulate cortex with a pseudo‐polycystic appearance on neuroimaging. Histological features contained the “specific glioneuronal element” mimicking DNT and the components of distinct neurocytic rosettes with a center of neuropil islands and pilocytic astrocytoma resembling RGNT. Although the mechanisms of mixed glioneuronal tumor are far from being well‐known, their co‐existence might suggest a possible etiologic relationship between DNT and RGNT.     

Clinico‐pathological feature of pilomyxoid astrocytomas: Three case reports

Pilomyxoid astrocytoma (PMA) is a newly identified variant of pilocytic astrocytoma (PA). We report three cases of PMA with comparison to seven cases of PA in terms of their clinicopathological features. The three cases occurred at the ages of 2, 36 and 6 years, and their tumors were located in the left basal ganglia, the pineal gland, and the cerebellum, respectively. They were diagnosed PMA by surgical specimens that showed a characteristic monomorphous architecture with an angiocentric growth pattern and myxoid background. One patient developed localized relapse at 6 months after the surgery, but the other patients remained alive without tumor progression more than 5 years after treatment. In analysis of the immunohistochemical association in PMA and PA, no specific staining was found to be useful for differential diagnosis of PMA from PA. The expression of biomarkers including O‐6‐methylguanine‐DNA methyltransferase, p53, MIB‐1, and EGF receptor neither distinguished PMA from PA nor correlated with outcome. But almost all PMA and PA that demonstrated prominent positivity for nestin showed a high MIB‐1 labelling index (LI), and four of these five patients suffered a relapse in the early phase. These results suggest that immunohistochemical expression of nestin and MIB‐1 LI may correlate with the aggressiveness of the tumor in PA and PMA.     

Anaplastic pilocytic astrocytoma

This clinical series examines the presentation of three adult patients who were found to have de novo anaplastic pilocytic astrocytoma. Initial imaging demonstrated an intracranial mass with histological analysis diagnostic of pilocytic astrocytoma with anaplastic features including necrosis, marked nuclear pleomorphism and a very high mitotic rate leading to the diagnosis of anaplastic pilocytic astrocytoma. We discuss the clinical pitfalls, treatment and implications when managing this condition.     

BCR gene disruption in a pilomyxoid astrocytoma

We report here a 4‐month‐old child with a large, solid enhancing mass involving predominantly the suprasellar and diencephalic regions, with extension of both hemispheres. The patient underwent partial resection of the mass by right temporal craniotomy. Histological diagnosis was of a low‐grade glioma consistent with pilomyxoid astrocytoma. Cytogenetic analyses revealed an insertion on chromosome 17 that involved disruption of the BCR gene. This finding suggests a possible rearrangement of this gene that could act in a similar way to chronic myeloid leukemia with formation of a chimeric tyrosine kinase protein. This study may suggest the use of inhibitors of tyrosine kinase proteins as an alternative treatment approach in cases of refractory or disseminated pilocytic astrocytomas.     

KIAA0510, the 3′‐untranslated region of the tenascin‐R gene,and tenascin‐R are overexpressed in pilocytic astrocytomas

I. El Ayachi, N. Baeza, C. Fernandez, C. Colin, D. Scavarda, P. Pesheva and D. Figarella‐Branger (2010) Neuropathology and Applied Neurobiology 36, 399–410
KIAA0510, the 3′‐untranslated region of the tenascin‐R gene, and tenascin‐R are overexpressed in pilocytic astrocytomas Aims: Studying the molecules and signalling pathways regulating glioma invasiveness is a major challenge because these processes determine malignancy, progression, relapse and prognosis. We took advantage of our previous study focused on genes that were critical in tumour invasion to further study here an unknown sequence, referred to as KIAA0510, the chromosomal location of which was 1q25, described as a 5596‐bp long mRNA and that we found to be significantly overexpressed in pilocytic astrocytomas compared with glioblastomas. Methods and results: Using in silico analysis as well as Polymerase chain reaction techniques, we decipher the full genomic characterization of the KIAA0510 sequence and demonstrate that KIAA0510 constitutes the 3′‐untranslated region of tenascin‐R gene. We have clearly confirmed the overexpression of tenascin‐R in pilocytic astrocytomas vs. glioblastomas at mRNA and protein levels. We also analysed a large series of various brain tumours and found that in the group of astrocytic tumours, tenascin‐R expression decreased with malignancy, whereas oligodendrogliomas sometimes retained a high level of tenascin‐R even in high‐grade tumours. Gangliogliomas strongly expressed tenascin‐R too. In contrast, ependymomas and meningiomas were negative. In normal brain, tenascin‐R was exclusively expressed by normal oligodendrocytes and subsets of neurones during post‐natal development and in adulthood, where it could differentially affect cellular adhesiveness and/or differentiation. Conclusion: KIAA0510, the 3′‐untranslated region of the tenascin‐R gene, and tenascin‐R are overexpressed in pilocytic astrocytomas. Gangliogliomas shared with pilocytic astrocytomas strong tenascin‐R expression. Whether tenascin‐R overexpression negatively influences brain invasion remains to be determined.     

Juvenile pilocytic astrocytoma 'pilomyxoid variant' with spinal metastases.

We report a case of juvenile pilocytic astrocytoma of the hypothalamic/chiasmatic region with cerebrospinal fluid dissemination in a 16-month old girl. The tumour in this case had unusual histological features including the abundance of myxoid background, the absence of Rosenthal fibres and the presence of an angiocentric pattern. These features are consistent with the recently described "variant" named pilomyxoid astrocytoma. It remains unclear whether pilomyxoid astrocytoma represents an aggressive variant of classical juvenile pilocytic astrocytoma, or an entirely distinct clinico-pathological entity. Larger series and new molecular techniques may answer this question in the future.     

Dissemination patterns of pilocytic astrocytoma

Two patients with multifocal pilocytic astrocytoma diagnosed by magnetic resonance imaging (MRI) and confirmed by histopathological examination are reported. They presented distinct sites and mechanisms of metastasis: to distant ventricles through the cerebral spinal fluid (CSF) in patient 1 and to contralateral parenchyma, possibly through white matter tracts, in patient 2, a pathway not so far reported in pilocytic astrocytoma. Early detection of multifocal pilocytic astrocytoma by MRI may change treatment strategies and improve prognosis.     

Cortical ependymoma or monomorphous angiocentric glioma?

Ependymoma is the third most common childhood intracranial tumor after medulloblastoma and pilocytic astrocytoma. Most ependymomas occur in the posterior fossa and spinal cord but only five cases confined to the cerebral cortex have been reported. The current case is a 5‐year‐old boy with a somewhat ill‐defined cortical tumor diagnosed as pilocytic astrocytoma on biopsy, and treated with radiotherapy. Nine years later, resection of the essentially unaltered tumor was performed for treatment of intractable seizures. Histologically, the tumor had some areas with the typical appearance of ependymoma as well other areas which contained piloid cells. There was also evidence of focal infiltrative growth. These findings bore resemblance to a recently described entity monomorphous angiocentric glioma/angiocentric neuroepithelial tumor, which combines features of ependymoma with pilocytic and diffuse astrocytomas. Both cortical ependymomas and angiocentric monomorphous glioma/angiocentric neuroepithelial tumor appear to be low‐grade tumors although their rarity makes accurate prognosis problematic. The current case has features of both entities, suggesting they may be closely related.     

Advanced reactive astrogliosis associated with hemangioblastoma versus astroglial-vascular neoplasm ("angioglioma")

Hemangioblastomas of the central nervous system are often accompanied by a cyst exhibiting an extensive astroglial reaction. The cyst's wall might be composed of various astroglial elements including reactive pilocytic or gemistocytic and hypertrophic astrocytes. The small tissue samples composed of compact gliotic tissue are sometimes nonrepresentative for primary hemangioblastoma tumour and might be confused with both pilocytic and diffuse infiltrative astrocytoma. Moreover, vascular anomalies of hemangioblastoma-like pattern could be combined with true neoplastic glial proliferation. Such association of glioma with certain types of vascular anomalies has been designated as angioglioma. In the current study we evaluated a series of hemangioblastomas accompanied by advanced astrogliosis of adjacent brain tissue. In some cases the histopathological features of pilocytic gliosis with numerous Rosenthal fibres and eosinophilic granular bodies strongly suggest the diagnosis of pilocytic astrocytoma. One tumour was identified as an angioglioma exhibiting a combination of hemangioblastoma-like tissue and pilocytic astrocytoma. The recognition of such an entity is important in differential tumour diagnosis and prognosis.     

Hemosiderin pigmentation of tumour cells in cerebellar pilocytic astrocytoma associated with post-traumatic hemorrhage in adults

The pilocytic astrocytoma is only rarely associated with gross intratumoral hemorrhage despite rich vasculature and blood vessel changes, accompanied often by perivascular depots of hemosiderin. We report an unusual case of pigmented cerebellar pilocytic astrocytoma presenting with posttraumatic hemorrhage in a 38-year-old man with no history related to the tumor. CT and MRI examination after head injury demonstrated unexpectedly the cystic lesion of 2 cm in diameter in the region of the right cerebellar hemisphere and vermis. The lesion was associated with hematoma and it was surgically removed 3 weeks after trauma. Histopathological examination revealed pilocytic astrocytoma tissue with broad hemorrhagic changes and with an unusual pattern of massive pigmentation of the cytoplasm of pilocytic astrocytes, consistent with hemosiderosis. Positive stains for iron and ferritin and ultrastructural study confirmed deposition of hemosiderin granules in the tumour cells. There was no evidence of melanin or melanosomes. This finding of hemosiderin accumulation in the cytoplasm of neoplastic astroglia seems to be analogous to post-hemorrhagic pigmentation of the normal Bergmann glia and subpial astrocytes. In the literature, the examples of neuroepithelial tumors with hemosiderin pigmentation of tumor cells have been rarely documented. To our knowledge, this is the first reported case of pigmented pilocytic astrocytoma exhibiting extensive intracellular hemosiderin deposition.