Christian H. Rickert

Cell death mechanisms in multiple system atrophy.

The presence and distribution of apoptotic cell death in multiple system atrophy (MSA) and morphologically related diseases were investigated by means of a modified terminal deoxynucleotidyl transferase-mediated nick end labeling method, comparing their distribution with that of glial cytoplasmic inclusions, immunohistochemically demonstrated bcl-2 protein, bax protein, CD95, TNFα, and p53-protein expression, as well as activated microglia. Apoptosis occurred almost exclusively in oligodendrocytes in multiple system atrophy and its general distribution was comparable to the already known oligodendroglial pathology in this disorder. Additionally, in about a quarter of glial cytoplasmic inclusions, there was upregulation of bcl-2-protein and coexpression with ubiquitin, suggesting a final attempt of involved cells to counteract apoptotic cell death. Bax protein was also demonstrated in oligodendroglial cells. A significant neuronal apoptosis was not observed in MSA; these cells might be destroyed secondarily to oligodendroglial apoptosis by necrosis or other forms of programmed cell death. These results emphasize the central role of oligodendroglial pathology in multiple system atrophy, making this disease unique among neurodegenerative diseases.

Prognostic Implications of Atypical Histologic Features in Choroid Plexus Papilloma

The prognostic significance of atypical histologic features in choroid plexus tumors remains uncertain. Therefore, a series of 164 choroid plexus tumors was evaluated for the presence of atypical histologic features, including mitotic activity, increased cellularity, nuclear pleomorphism, blurring of papillary growth pattern, and necrosis. The impact of histopathologic and clinical features on the probability of recurrence and survival was investigated. Twenty-four tumors displaying frank signs of malignancy were diagnosed as choroid plexus carcinoma according to World Health Organization criteria. Of 124 choroid plexus papillomas that had not received adjuvant treatment, 46 tumors (37%) displayed at least one atypical feature, including increased cellularity (n = 25 [20%]), mitotic activity (≥2 mitoses per 10 high-power fields; n = 19 [15%]), nuclear pleomorphism (n = 16 [13%]), solid growth (n = 15 [12%]), and necrosis (n = 5 [4%]). Only one tumor-related death, but 10 recurrences, were observed on a mean observation time of 58 months. On univariate analysis, incomplete surgical resection (p = 0.03) and mitotic activity (p < 0.001) were the only clinicopathologic factors associated with recurrence. Using a multivariate model, an independent effect of mitotic activity on the probability of recurrence could be confirmed (p = 0.001). Because mitotic activity is the sole atypical histologic feature independently associated with recurrence, we propose to define atypical choroid plexus papilloma by mitotic activity (≥2 mitoses per 10 high-power fields) corresponding to World Health Organization grade II, thus adjoining other intermediate tumor entities associated with increased mitotic activity such as atypical meningioma. Close follow up of patients harboring atypical choroid plexus papillomas may be warranted.

Imprinted CDKN1C is a tumor suppressor in rhabdoid tumor and activated by restoration of SMARCB1 and histone deacetylase inhibitors.

SMARCB1 is deleted in rhabdoid tumor, an aggressive paediatric malignancy affecting the kidney and CNS. We hypothesized that the oncogenic pathway in rhabdoid tumors involved epigenetic silencing of key cell cycle regulators as a consequence of altered chromatin-remodelling, attributable to loss of SMARCB1, and that this hypothesis if proven could provide a biological rationale for testing epigenetic therapies in this disease. We used an inducible expression system to show that the imprinted cell cycle inhibitor CDKN1C is a downstream target for SMARCB1 and is transcriptionally activated by increased histone H3 and H4 acetylation at the promoter. We also show that CDKN1C expression induces cell cycle arrest, CDKN1C knockdown with siRNA is associated with increased proliferation, and is able to compete against the anti-proliferative effect of restored SMARCB1 expression. The histone deacetylase inhibitor (HDACi), Romidepsin, specifically restored CDKN1C expression in rhabdoid tumor cells through promoter histone H3 and H4 acetylation, recapitulating the effect of SMARCB1 on CDKNIC allelic expression, and induced cell cycle arrest in G401 and STM91-01 rhabdoid tumor cell lines. CDKN1C expression was also shown to be generally absent in clinical specimens of rhabdoid tumor, however CDKN1A and CDKN1B expression persisted. Our observations suggest that maintenance of CDKN1C expression plays a critical role in preventing rhabdoid tumor growth. Significantly, we report for the first time, parallels between the molecular pathways of SMARCB1 restoration and Romidepsin treatment, and demonstrate a biological basis for the further exploration of histone deacetylase inhibitors as relevant therapeutic reagents in the treatment of rhabdoid tumor.

Congenital immature teratoma of the fetal brain

Abstract Congenital intracranial tumors are very rare and only account for 0.5–1.5% of all childhood brain tumors. Even rarer are those with prenatal manifestation. The most common of these present at birth are teratomas, which show divergent differentiation with 90% of them containing tissues from all three germ layers. We report a rare case of an intrauterine congenital immature teratoma in a female fetus at 23 weeks of gestation, which was sonographically diagnosed in vivo by detection of the tumor and associated craniomegaly. Because of the poor prognosis, termination of the pregnancy was induced by Rivanol instillation. The cerebral tumor was confirmed at autopsy and was not associated with any other malformations. Histological and immunohistochemical features of this tumor are presented.

Abdominal metastases of pediatric brain tumors via ventriculo-peritoneal shunts.

Abstract Internal drainage of cerebrospinal fluid (CSF) to the abdominal cavity via a ventriculo-peritoneal shunt (VPS) is a procedure that is commonly used for the treatment of obstructive hydrocephalus. As this condition is often caused by brain tumors blocking the natural CSF pathways, a VPS, as an artificial anastomosis, can provide the means for tumor cells to be spread with the CSF. A review of the literature reveals 35 VPS-related abdominal metastases from pediatric brain tumors; 17 in patients aged 0–9 (group A) and 18 in patients aged 10–18 years (group B); the mean age of male patients was 10.5, and that of female patients, 7 years. The male-to-female ratio was 1.9 (group A 1.1, group B 3.5), and the mean interval between shunt operation and diagnosis of metastases, 16.7 months (group A 11.6, group B 22.6 months; boys 21.6, girls 7.5 months). During the observation period, 22/30=73.3% of the patients died (group A 13/15=86.7%, group B 9/15=60%; boys 13/21=61.9%, girls 9/9=100%); their mean survival time after shunting was 18.7 months (group A 15.7, group B 23.1 months; boys 25.5, girls 9 months). The four most common sources of metastases were germinomas (9 cases=25.7%; group A none, group B 9), medulloblastomas (8 cases=22.9%, group A 7, group B 1), endodermal sinus tumors (5 cases=14.3%, group A 1, group B 4), and astrocytomas (4 cases=11.4%, group A 4, group B none). Metastases via VPS are rare, but should be considered as a possible complication and mode of systemic spread in children with primary intracranial malignancy. They have a more favorable prognosis in boys and in the second decade of life.

Chromosomal imbalances in clear cell ependymomas

Clear cell ependymoma is a rare and diagnostically challenging subtype of ependymoma, whose genetic features are essentially unknown. We studied 13 clear cell ependymomas (five cases WHO grade II, eight cases WHO grade III) by comparative genomic hybridization (CGH). Chromosomal imbalances were found in 12/13 cases. The most common aberrations overall were +1q (38%), −9 (77%), −3 (31%), and −22q (23%). Clear cell ependymomas of WHO grade II were characterized by −9 (40%), whereas WHO grade III cases mainly showed +1q (63%), and +13q (25%), as well as −9 (100%), −3 (38%), and −22q (25%). In contrast to other ependymal tumors, clear cell ependymomas of WHO grade II showed fewer imbalances than WHO grade III samples (1.4 vs 3.5 per case). Although some of the implicated chromosomes have previously been shown to be involved in other ependymoma variants, the striking frequency of +1q, −9, and −3 suggests that aberrations differ between clear cell and other types of ependymomas, in particular, for loss of chromosome 9 which can be regarded as the molecular hallmark of clear cell ependymomas.

Epidemiological features of brain tumors in the first 3 years of life

Abstract We investigated the age-related location, gender distribution, and histology of 75 brain tumors in children under 3 years of age seen in our department between 1984 and 1997. These were characterized by a higher overall incidence in boys (42/33 cases; ratio 1.3) and a prevalence for a supratentorial location (48/27 cases; ratio 1.7); the most common histological entities were astrocytoma (25.3%) and ependymoma (17.3%), followed by medulloblastoma (13.3%) and PNET (10.8%); 44% were high-grade tumors corresponding to WHO grades III and IV. In the 1st (22 cases), 2nd (25 cases) and 3rd (28 cases) years of life, the boy–girl ratios were 1.0, 1.5 and 1.3, respectively, while there was a decrease with age in the frequency of supratentorial (ratios 3.4, 1.1, and 1.2) and high-grade tumors (77.3%, 36.0%, and 32.1%). In the 1st year of life the most common neoplasms were PNETs (22.7%) and in the 2nd year both astrocytomas and ependymomas (24.0% each); astrocytomas (35.7%) prevailed in the 3rd year of life.

Frequent but borderline methylation of p16 (INK4a) and TIMP3 in medulloblastoma and sPNET revealed by quantitative analyses.

Certain risk groups among tumors of the central nervous system (CNS) in children take an almost inevitably fatal course. The elucidation of molecular mechanisms offers hope for improved therapy. Aberrant methylation is common in malignant brain tumors of childhood and may have implications for stratification and therapy. Methylation of p16INK4A, p14ARF, TIMP3, CDH1, p15INK4B and DAPK1 in medulloblastoma (MB) and ependymoma has been discussed controversially in the literature. DUTT1 and SOCS1 have not previously been analyzed. We examined methylation in MB, sPNET and ependymoma using methylation-specific PCR (MSP), quantitative Combined Bisulfite Restriction Analysis (COBRA) and direct and clone sequencing of bisulfite PCR products. We detected methylation of p16INK4A (17/43), p14ARF (11/42) and TIMP3 (9/44) in MB and others by MSP. CDH1 was not only methylated in MB (31/41), but also in normal controls. Evaluation of MSP results by quantitative COBRA and sequencing yielded methylation between the detection limits of COBRA (1%) and MSP (0.1%). Only p16INK4A and TIMP3 were methylated consistently in medulloblastomas (p16INK4A 14%, TIMP3 11%) and p16INK4A also in anaplastic ependymomas (1/4 tumors). Methylation ranged from 1–5%. Evaluation of methylation using MSP has thus to be supplemented by quantitative methods. Our analyses raise the issue of the functional significance of low level methylation, which may disturb the delicate growth factor equilibrium within the cell. Therapeutic and diagnostic implications urge into depth analyses of methylation as a mechanism, which might fill some of the gaps of our understanding of brain tumor origin.

Rosetted glioneuronal tumour of the spine: clinical, histological and cytogenetic data

Since the appearance in 2000 of the World Health Organization classiWcation for central nervous system neoplasms [5], numerous descriptions of new entities or variants have appeared in the literature. In the group of neuronal and mixed glioneuronal neoplasms are lesions with distinctive morphological features that are still not included in a precise classiWcation (for a review see [1]). Glioneuronal tumours with neuropillike islands (“rosetted glioneuronal tumours”) were reported a few years ago as a novel brain tumour entity with characteristic clinico-pathological features [10]. The initial report comprised four adult patients with supratentorial cerebral hemispheric masses with associated seizures. Since then, two more supratentorial adult cases have been added to the literature [4, 7], one of them in this journal by one of the current authors which also showed DNA copy number aberrations detected by comparative genomic hybridisation (CGH), consisting of a gain of chromosome 7q21.1qter and loss of 9p21-pter [4]. All tumours were shown to be inWltrative in their histological growth pattern and predominantly glial in appearance, being composed mainly of Wbrillary, gemistocytic, or protoplasmic astroglial elements. Their distinguishing feature was their content of sharply delimited, neuropil-like islands of intense synaptophysin reactivity inhabited and rimmed in rosetted fashion by cells demonstrating strong nuclear immunolabeling for the neuronal antigen NeuN. So far, only two cases of a spinal glioneuronal tumour with rosetted neuropil-like islands have been presented, consisting of a 44-year-old woman with recurrence and dural dissemination a year later [2] and an 8-year-old boy with possible recurrence and diVuse leptomeningeal enhancement after one year of follow-up [9]. Here we present additional cytogenetic data of a spinal case of rosetted glioneuronal tumour encountered in a 16-year-old girl. The patient had suVered from therapy-resistant back pain of the cervico-thoracic junction for several months. Upon radiographic imaging a contrast-enhancing intramedullary tumour was found spanning the length of the spinal cord from C7 to T2 with proximal cystic widening of the myelon reaching C3 (Fig. 1). The tumour could be resected completely. One year after the operation the patient still suVered from left sided plantar extensor paralysis; however, a repeat MRI showed no remaining or recurrent tumour. Histologically, the mass presented as a moderately cellular neuroectodermal tumour. Notable features of the lesion were paucicellular, Wbrillary and round rosette-like structures alternating with cellular areas devoid of rosettes (Fig. 2a). The rim of the rosettes was formed by aligned round to oval chromatin-rich nuclei in a satellite-like fashion. No perivascular pseudorosettes or necroses were seen, and the mitotic rate was C. H. Rickert (&) Department of Anatomical Pathology, Royal Children’s Hospital Melbourne, Flemington Road, Parkville , Melbourne, 3052, VIC, Australia e-mail: christian.rickert@rch.org.au

Cortical dysplasia: neuropathological aspects

IntroductionMalformations of the cerebral cortex are a frequent cause of pharmacoresistant epilepsies and developmental disorders.Epidemiology and geneticsThe incidence of cortical dysplasias in epilepsy surgical series varies from 12 to 40% and focal cortical dysplasias (FCD) are one of the most common neuropathological findings in resection specimens from pediatric patients undergoing cortical resections for the treatment of refractory epilepsy.Macroscopy and histopathologySurgical specimens in FCD may appear normal macroscopically, but in some cases, widening of the cortex with poor demarcation from the underlying white matter is noted. In milder dysplasias, the main pathological feature is disorganization of the cortical architecture (“dislamination”) with less striking neuronal and glial cytopathology. Histopathology shows an excess of neurons in layer I, including Cajal–Retzius cells, clusters of neurons, marginal glioneuronal heterotopias, and a persistent subpial granule cell layer. The hallmarks of FCD are disorganization of the laminar architecture and of the cytology of individual neurons. In many cases, layer I remains hypocellular and distinct from deeper laminae, but lower cortical layers may be ill-defined or broken up by the presence of many large and randomly located abnormal and cytomegalic neurons; depending on their morphology, referred to as “giant neurons,” “immature neurons,” or “dysmorphic neurons.” The other pathognomonic cell type associated with FCD is the “balloon cell.” These cells were originally considered to be of astrocytic lineage; however, there is evidence that they are in effect “balloon neurons.”Immunohistochemistry and structural findingsImmunohistochemistry is not essential in making the diagnosis of FCD or microdysgenesis but allows further characterization of cell types.