Pulsed arterial spin labeling applications in brain tumors: practical review

Few institutions use MRI perfusion without contrast injection called arterial spins labeling (ASL) routinely in clinical setting. After general considerations concerning the different ASL techniques and quantitative issues, we will detail a pulsed sequence that can be used on a clinical 1.5-T MR unit. We will discuss and illustrate the use of ASL in tumoral diseases for diagnosis, gliomas grading, stereotactic biopsy guidance and for follow-up after treatment.

[Thoracic aortic dissection revealed by systemic cholesterol embolism]

Systemic cholesterol embolism is a rare complication of atherosclerosis, and has various presentations. Arterial catheterisms are a common cause. However, the association with an aortic dissection has been exceptionally reported. We report the observation of a 70 year-old man, with coronary artery disease, hypertension, diabetes and dyslipidemia. Six months before hospitalization, a coronary angioplasty was performed due to recurrent angina. The association of purpuric lesions on the feet, with acute renal failure confirmed cholesterol embolism syndrome. Transoesophageal echocardiography showed a dissection of the descending thoracic aorta associated with complex atheroma. The evolution was marked by the pulpar necrosis of a toe and by a worsening of the renal failure, requiring definitive hemodialysis. Further echographic control highlighted the rupture of the intimal veil of the dissection. Cholesterol embolism syndrome may reveal an aortic dissection in patients without thoracic symptoms. In such cases, transoesophageal echocardiography is a useful and non-invasive examination.

[Criteria of diagnosis and grading of oligodendrogliomas or oligo-astrocytomas according to the WHO and Sainte-Anne classifications]

Two main classification systems are used in France for the histological typing and grading of oligodendrogliomas: the WHO and Sainte-Anne Hospital (SA) classifications. According to the WHO, the typing of diffuse gliomas is based on the predominant cell type, oligodendroglial versus astrocytic. In contrast, the SA classification is based on the distinction of two patterns of tumor growth, solid tumor tissue versus isolated tumor cells and also relies on imaging and clinical features. According to this approach, the SA classification includes in the category of oligodendrogliomas, the fibrillary or gemistocytic diffuse astrocytomas (WHO grade II) as well as a substantial proportion of astrocytomas WHO grade III, 2) the WHO uses multiple histological criteria for the grading of oligodendrogliomas (grade II versus grade III), including the degree of differentiation, cellular atypia, mitotic activity and necrosis. In contrast, the SA grading of these tumors (grade A versus B) only uses two criteria: the presence or absence of endothelial hyperplasia, and the presence or absence of contrast enhancement. This last criterion allows overcoming the problems related to the representativeness of surgical samples. Difficulties and discrepancies regarding the diagnosis of oligodendrogliomas are in part due to the lack of immunomarker for the identification of tumoral oligodendrocytes. The potential interest of new markers of oligodendroglial precursors for the diagnosis of these tumors will further be discussed.

[Reappraisal of the Sainte-Anne Hospital classification of oligodendrogliomas in view of retrospective studies]

PURPOSE

Definition of homogeneous tumor groups of oligodendrogliomas or oligo-astrocytomas is a basic condition for an adequate evaluation and comparison of the results of treatments in patients from various institutions. However, increasing discordances are observed in the histological diagnosis of these tumors. The main goal of this study is to assess whether, for retrospective studies, MRI data may serve as a common basis for encompassing asymmetry in diagnosis established according to the WHO or Ste-Anne (SA) classification.

PATIENTS AND METHODS

This study included 251 adult patients in whom a SA grade A or B oligodendroglioma or oligo-astrocytoma was newly diagnosed at our institution from 1984 to 2003. Routine histological preparations and post-contrast preoperative MRI/CT-scan were simultaneously reviewed in order to assess the impact on survival of the following features: presence or absence of a polymorphous or gemistocytic astrocytic component, of necrosis and of contrast enhancement (CH); endothelial hyperplasia (EH) assessed as absent, present minor (HE+) or (HE++) when conform to the threshold of HE defined in the SA grading system of oligodendrogliomas. The tumors were graded A: no CH and no EH; in B: CH and /or HE++, and A/B: EH + but no CE.

RESULTS

70.1% of the tumors were classified as "pure" oligodendroglioma, 19.5% as "polymorphous oligo-astroastrocytoma" and 10.3% as "gemistocytic oligo-astrocytoma". In grade A, or B tumors, the presence of a polymorphous or a gemistocytic component had no significant influence on survival; however respectively 53% and 65% of these tumours versus 32% of "pure" oligodendrogliomas were grade B at the time of diagnosis. In either histological subtypes, survival was not significantly different when HE was absent or minor (HE+). After regrouping of the histological subtypes and of the tumors with HE+ or absent, the series included 153 oligodendrogliomas grade A and 98 grade B. Survival in patients with grade A versus grade B tumors was respectively 142 versus 52 months (p<0.0001). In grade B tumors, necrosis had no significant influence on survival. Ring-shaped contrast enhancement surrounding large foci of necrosis was observed in only 4 cases. In tumors with or without CE, patient survival was respectively 148 versus 40 months (p<0.0001). On post contrast MRI done in 235 patients, only 7 tumors (3%) were grade A/B (EH++ but no CH).

CONCLUSIONS

From these results and our previous observation that, according to the SA classification of gliomas, only oligodendrogliomas or oligo-astrocytomas may not show CE, we propose that for retrospective studies: 1) tumors diagnosed according to the Ste-Anne classification as oligodendroglioma or oligo-astrocytoma be regrouped in a unique category, 2) independent of their histological type and grade according to the WHO, gliomas that do not show CE be regrouped with SA oligodendrogliomas grade A, 3) concerning gliomas that show CE on MRI: oligodendrogliomas or oligo-astrocytomas WHO grade II or III, as well as WHO secondary glioblastomas or glioblastomas with an oligodendroglial component, be regrouped with SA oligodendrogliomas grade B; however tumors that show ring-like CE surrounding large foci of necrosis and finger-like "peritumoral" edema should be excluded or analysed separately.

[Oligodendrogliomas: historical background of classifications]

The story of the classifications for gliomas is related to the development of the techniques used for cytological and histological examination of brain parenchyma. After a review of these techniques and the progressive discovery of the central nervous system cell types, the main classifications are presented. The first classification is due to Bailey and Cushing in 1926. It was based on histoembryogenetic theory. Then Kernohan introduced, in 1938, the concept of anaplasia. The WHO classification was published in 1979, then revised in 1993 and 2000. It took into account some data from both previous systems and introduced gradually the notion of histological criteria of malignancy. More recently; molecular genetics data and clinical evolution were retained. The Sainte-Anne classification for oligodendrogliomas is based on both histological and imaging data. It includes the notion of spatial histological structure of oligodendrogliomas. Contrast enhancement is closely related to endotheliocapillary hyperplasia. Gliomas classifications are changing and confusions can be made because of lack of reproductibility and misinterpretations of samples.

[Histology and oligodendrogenesis of glial cells]

Oligodendrogenesis is a complex and dynamic phenomenon. Knowledge of the underlying molecular control mechanisms advances steadily, especially in rodents. While the parallelism with human oligodendrogenesis is not fully established, the main characteristics are recognized. Neuroepithelial cells of the neural tube participate in both gliogenesis and neurogenesis. Oligodendrogenesis begins after neurogenesis and stops after birth. It is a focal phenomenon under the control of specific morphogenic proteins, and can generate precursors which are able to proliferate and migrate in the same time. Five steps of oligodendrogliogenesis follow one another acquiring and loosing proteinic markers. They lead to intricated maturation steps for generating myelinizing oligodendrocytes, NG2 cells and precursors of quiescient adult oligodendrocytes.

[Results of the Sainte-Anne - Lyons series of 318 oligodendroglioma in adults]

INTRODUCTION

Incidence of cerebral oligodendrogliomas is increasing because of better recognition made possible by improved classifications. We studied a homogeneous series using the Sainte-Anne grading scale in order to better understanding the history of these tumors with or without treatment and to assess prognosis and associated factors.

PATIENTS AND METHODS

A retrospective series of 318 adult patients with oligodendroglioma (OLG) treated at Hôpital Sainte-Anne, Paris (SA) and Hôpital Neurologique, Lyons (L) between 1984 and 2003 was analyzed: 182 grade A OLG (SA + L), 136 grade B among which a homogenous series of 98 (SA) were included. For grade A: age at diagnosis ranged from 21 to 70 (mean: 41), sex ratio was 1.28. For grade B: age at diagnosis ranged from 12 to 75 (mean: 45.5), sex-ratio was 1.58. The main first symptoms were: epilepsy (A: 91.5%; B: 76%), intracranial hypertension (A: 7.9%; B: 14.6%), neurological deficit (A: 5.1%; B: 17.7%). The most frequent locations were: frontal, insular and central for both A and B. Mean size was 55 mm for grade A, 62 mm for B. Calcifications were found in 20% of A, 48.5% of B. No tumor was enhanced on imaging (CT/MRI) in grade A, all but 7 in grade B. All patients underwent surgery either for biopsy (A: 47.2%; B: 53%), or removal which was partial (A: 26.4% vs B: 19.4%) or extended (A: 36.3% vs B: 37.8%). Fifty-six patients underwent 2 procedures and 12 three procedures. Radiotherapy was performed in 76.9% of grade A, and 91% of B patients, in the immediate postoperative period for 71% A and 82.7% B. Chemotherapy was delivered for 36% of grade A (in the event of transformation to grade B or failure of radiotherapy) and 67.5% of B patients. Among grade A tumors, 38% transformed into grade B within a mean delay of 51 months with a mean follow-up of 78 months.

RESULTS

Median survival was 136 months for grade A and 52 for grade B. Survival at 5, 10 and 15 was 75.5%, 51% and 22.4% for grade A vs 45.2%, 31.3% and 0% for grade B respectively. In univariate and multivariate analysis, grade A survival was associated with age at diagnosis, tumor size, large removal and response to radiotherapy. Grade B survival was associated with age at diagnosis, wide removal and sharply defined limits of the tumor on imaging.

CONCLUSIONS

Analysis of both published data and this series underlines many prognostic parameters. It shows that OLG are heterogeneous tumors even in each grade (A and B). Treatment should consequently progress towards more targeted procedures for patients mainly with postoperative radiotherapy and chemotherapy.

Suprasellar paraganglioma: a case report and review of the literature

Paragangliomas arising in the suprasellar region are extremely rare. We report a case of suprasellar paraganglioma in a 47-year-old man who presented with amnesia and impaired visual acuity without any endocrine dysfunction. Magnetic resonance imaging (MRI) showed a large enhancing tumour in the suprasellar area. Following subtotal surgical excision, the diagnosis of paraganglioma was confirmed by pathology. In this case report we describe the MRI pattern of suprasellar paraganglioma and review the literature of this uncommon lesion.

Functional endothelin ET B receptors are selectively expressed in human oligodendrogliomas

Endothelin-1 (ET-1), a vasoactive and mitogenic peptide mainly produced by vascular endothelial cells, may be involved in the progression of several human tumors. Here, we present an immunohistochemical analysis of the expression pattern of ET-1 receptor subtypes (ET(A)-R and ET(B)-R) and a functional study of their potential role in human oligodendrogliomas and oligoastrocytomas. By comparison, we assessed the corresponding expression patterns of glioblastomas. Interestingly, a nuclear localization of ET-1 receptor subtypes (associated or not with a cytoplasmic labeling) was constantly observed in tumor cells from all three glioma types. Moreover, we noted a distinct receptor distribution in the different gliomas: a nuclear expression of ET(B)-R by tumor cells was found to be restricted to oligodendrogliomas and oligoastrocytomas, while a nuclear expression of ET(A)-R was only detected in tumor cells from some glioblastomas. Using primary cultures of oligodendroglial tumor cells, we confirmed the selective expression of nuclear ET(B)-R, together with a plasma membrane expression, and further demonstrated that this receptor was functionally coupled to intracellular signaling pathways known to be involved in cell survival and/or proliferation: extracellular signal-regulated kinase and focal adhesion kinase activation, actin cytoskeleton reorganization. In addition, impairment of ET(B)-R activation in these cells by in vitro treatment with an ET(B)-R-specific antagonist induced cell death. These data point to ET-1 as a possible survival factor for oligodendrogliomas via ET(B)-R activation and suggest that ET(B)-R-specific antagonists might constitute a potential therapeutic alternative for oligodendrogliomas.

[Dysembryoplastic neuroepithelial tumors]

Dysembryoplastic neuroepithelial tumors DNTs are highly polymorphic tumors that arise during embryogenesis. They are preferentially, but not exclusively, located in the supratentorial cortex. Histologically they may mimic any categories of low-grade or even of high-grade gliomas, but from a carcinological point of view, they behave as stable lesions. Their differential diagnosis from gliomas is obviously important to spare these young patients with a normal life expectancy the long- term deleterious effect of radiation or chemotherapy. The diagnosis of DNT must be considered when all the following criteria are present: partial seizures with or without secondary generalization, no neurological deficit or a stable congenital deficit, cortical topography on MRI, absence of peri-tumoral edema and of mass effect. In other locations, the diagnosis of DNT has to be suspected in case of discordance between the neurological status of the patient and the topography of the tumor or of unusual radiological features such as contrast enhancement but no mass effect and no edema. Supratentorial cortical DNTs tend now to be detected more systematically by imaging soon after first seizures. In most instances, the epilepsy can be cured by gross total surgical removal. Surgery also allows to prevent the risks of intratumoral hematoma or infarct. DNTs should therefore be operated soon after diagnosis. However, excellent results can also be obtained by epilepsy surgery in patients with long term drug resistant partial seizures.

Brainstem gliomas in adults: prognostic factors and classification

In contrast to childhood brainstem gliomas, adult brainstem gliomas are rare and poorly understood. The charts of 48 adults suffering from brainstem glioma were reviewed in order to determine prognostic factors, evaluate the effect of treatment and propose a classification of these tumours. Mean age at onset was 34 years (range 16-70 years). The main presenting symptoms were gait disturbance (61%), headache (44%), weakness of the limbs (42%) and diplopia (40%). Four patterns were identified on MRI, representing non-enhancing, diffusely infiltrative tumours (50%), contrast-enhancing localized masses (31%), isolated tectal tumours (8%) and other patterns (11%). Treatment consisted of partial resection (8%), radiotherapy (94%) and chemotherapy (56%). Overall median survival was 5.4 years. On univariate analysis, the following favourable prognostic factors were identified (P< 0.01): age of onset <40 years, duration of symptoms before diagnosis >3 months, Karnofski performance status >70, low-grade histology, absence of contrast enhancement and 'necrosis' on MRI. On multivariate analysis, the duration of symptoms, the appearance of 'necrosis' on MRI and the histological grade of the tumour remained significant and independent prognostic factors (P< 0.05). Eighty-five percent of the tumours could be classified into one of the following three groups on the basis of clinical, radiological and histological features. (i) Diffuse intrinsic low-grade gliomas (46%) usually occurred in young adults with a long clinical history before diagnosis and a diffusely enlarged brainstem on MRI that did not show contrast enhancement. These patients were improved by radiotherapy in 62% of cases and had a long survival time (median 7.3 years). Anaplastic transformation (appearance of contrast enhancement, 27%) and relentless growth without other changes (23%) were the main causes of death. (ii) Malignant gliomas (31%) occurred in elderly patients with a short clinical history. Contrast enhancement and necrosis were the rule on MRI. These tumours were highly resistant to treatment and the patients had a median survival time of 11.2 months. (iii) Focal tectal gliomas (8%) occurred in young patients and were often revealed by isolated hydrocephalus. The course was indolent and the projected median survival period exceeded 10 years. In conclusion, adult brainstem gliomas are different from the childhood forms and resemble supratentorial gliomas in adults. Low-grade tumours have a clinicoradiological pattern that is so characteristic that the need for a potentially harmful biopsy is debatable. The optimum timing of treatment for supratentorial low-grade tumours remains unclear. In high-grade gliomas, the prognosis remains extremely poor despite aggressive treatment with radiotherapy and chemotherapy.

[Meningeal metastasis of pleural mesothelioma]

Meningeal metastases from malignant mesotheliomas are rarely observed. We report the case of a 54-year-old man with an asymptomatic pleural effusion and simultaneous sensitive and motor disorders of the right hemibody. A meningeal localization of a pleural malignant mesothelioma was discovered and confirmed by a comparative immuno-histological analysis. Here we present a differential diagnosis and a review of the literature to give prominence to diagnostic pitfalls in this rare disease.

Dysembryoplastic neuroepithelial tumors: CT, MR findings and imaging follow-up: a study of 53 cases

PURPOSE

To evaluate CT and MRI features and long term imaging follow-up of a large series of dysembryoplastic neuroepithelial tumors (DNTS).

PATIENTS AND METHODS

We retrospectively analyzed CT (100%) and MR imaging (83%) findings of 53 patients with complex (n = 14), simple (n = 6) or non specific histological forms (n = 33) of DNTS. All patients underwent epilepsy surgery for the treatment of drug resistant partial seizures. Preoperative radiological follow-up from two to 10 years (81%) and a post-operative follow-up from one to 13 years (92%) were available.

RESULTS

DNTs are intracortical tumors with no mass effect and no peritumoral edema. An associated deformity of the overlying skull was observed in 44% of the 34 patients with a cortical lesion of the convexity. We found a contrast enhancement of the lesion in 21% of cases, a calcic hyperdensity in 36% of cases and a cystic part in 7.5% of cases. DNTs were hypodense (82%) on CT examinations and had a decreased signal on the T1 Weighted Images (95%) and a hypersignal in T2 Weighted Images (100%) on MR imaging. Eighty-one percent of patients had a mean preoperative radiological follow-up of four years and the tumor was stable in size in all cases; 92% of patients had a mean post-operative radiological follow-up of 4.5 years and no recurrence was seen.

CONCLUSION

Three radiological features of DNTs are helpful for the diagnosis: cortical location, absence of mass effect and no surrounding edema. Clinical, radiological and histopathological findings have to be considered together in order to assess the diagnosis and to differentiate DNTs, which are stable lesions from gliomas.

[Parenchymal changes after radiosurgery of cerebral arteriovenous malformations. Clinical and MRI data]

BACKGROUND AND PURPOSE

Purposes of this study are to describe different parenchymal changes seen after radiosurgery of cerebral arteriovenous malformations and the clinical symptoms which can be associated, and risk factors correlated with them.

PATIENTS

and method. From the whole population of 705 patients with a cerebral arteriovenous malformations treated by radiosurgery between 1984 and 1998, clinical from 615 patients and post radiosurgery MRI data from 367 patients were reviewed. Neurological deficit occurred in 5.37% of cases and was still persistant in 1.46% of cases. Delay of occurrence of deficits ranged from 6 to 83 months (mean: 27 months, median: 15 months). Parenchymal changes seen in MRI were classified in 4 grades: 1 without parenchymal changes, 2 hypersignal in sp T2, 3=2 with homogenous enhancement with gadolinium, 4 with hyposignal in spT1 and annular irregular enhancement. Several parameters (size, volume, angioarchitecture of the cerebral arteriovenous malformation, dosimetric parameters) were studied and correlations were searched by uni and multivariate analysis with occurrence and delay of occurrence of deficits or parenchymal changes.

RESULTS

In multivariate analysis, only size was significantly correlated with occurrence of parenchymal changes (p=0.0016); only size of the malformation was significantly correlated with delay of occurrence of parenchymal changes (p=0.0082); only grade 4 was correlated with occurrence of neurological deficit (p<0.00001). However, when only "a priori" parameters (known before radiosurgery) are introducted in logistic model, size taille (p=0.02) and hypoplasy of a sinus (p=0.0049) are significantly correlated with occurrence of neurological deficit. Only parenchymal changes grade 4 was significantly correlated with delay of occurrence of a neurological deficit (p<0.00001). However, when only a priori parameters (known before radiosurgery) are introducted in logistic model, only arterial steal (p=0.054) was significantly correlated with delay of occurrence of a neurological deficit.

CONCLUSION

Parenchymal changes are various in expression, signification and clinical symptoms associated with them. They must be known and recognized for better prevention and symptomatic treatment as well.

[The "smears" technique for the extemporaneous examination: diagnostic contribution to neurosurgical pathology]

Smear preparation is a fairly accurate, simple and reliable tool for rapid intraoperative diagnosis of central nervous system tumors. Compared with frozen sections this technique has the advantage of being both more accurate for cytological details and of requiring less tissue. In addition final histological analysis after direct formalin fixation is of better quality than post freezing fixation. This technique is most helpful in the field of neuro-oncological pathology specially in glial tumors and in stereotactic biopsy procedures. The cytological aspects and smear patterns disclose important complementary diagnostic information for the histopathological examination.

Vascular endothelial growth factor expression in oligodendrogliomas: a correlative study with Sainte-Anne malignancy grade, growth fraction and patient survival

Microangiogenesis is a delayed but crucial event in the malignant progression of oligodendrogliomas. Accord-ingly, in the new Sainte-Anne grading system of oligodendrogliomas, endothelial hyperplasia and contrast enhancement, both being indicators of microangiogenesis, are key criteria for the distinction of grade A from grade B tumours. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor: a strong correlation between VEGF expression, Sainte-Anne malignancy grade and patient outcome might thus be expected. In order to assess this hypothesis, VEGF immunostaining was performed in a series of 34 oligodendrogliomas that included 11 grade B and 23 grade A, of which nine became grade B during the study period (mean clinical and imaging follow-up: 41 months). VEGF expression correlated strongly with Sainte-Anne tumour grade (P < 0.001), and inversely with patient survival (P < 0.001) and recurrence-free survival (P = 0.002). One hundred per cent of grade B but only 17% of grade A were VEGF-positive. By contrast, the MIB-1 labelling index did not correlate with VEGF expression, total survival or recurrence-free survival. In accordance with the grading system, this study showed that, in oligodendrogliomas, VEGF expression and microangiogenesis are progression-related phenomena that confer on these tumours a growth advantage by presumably reducing hypoxia-induced apoptotic cell death. These findings might have important implications in the future for the indication and timing of anti-angiogenic therapies.

Stereoelectroencephalography in focal cortical dysplasia: a 3D approach to delineating the dysplastic cortex

Focal cortical dysplasia (FCD) is an increasingly recognized cause of intractable epilepsy. Surgical data suggest that the dysplastic cortex should be removed to obtain freedom from seizures, but the prognosis remains poor as FCD is difficult to delineate by imaging. We retrospectively analysed a series of 28 patients (aged 5-41 years, median 16.5 years) with FCD who had been investigated by stereoelectroencephalography (SEEG) between 1964 and 1995. Neurophysiological data were correlated with histological findings and surgical outcome. MRI was available for only seven patients. Severe partial epilepsy of early onset, pre-existing neurological deficit (68%) and cognitive impairment were the main clinical features. FCD was distributed equally between all lobes except for the temporal lobe, and was found predominantly on the mesial aspect of the cerebral hemispheres. SEEG findings provided evidence of dysplastic tissue epileptogenicity, as demonstrated by intralesional rhythmic spike discharges, the onset of ictal discharges and a low epileptogenic threshold. The epileptogenic zone corresponded to histologically defined FCD in 82% of the cases. Despite the lack of adequate neuroimaging in most cases, 64% of the patients became seizure-free after surgery. The main predictors of a favourable outcome were complete removal of the epileptogenic zone (P< 0.01) and complete removal of the dysplastic cortex (P< 0.01). These results emphasize the usefulness of neurophysiological data in accurately assessing the extent of the FCD.

[High grade (B) oligodendroglioma. Concerns and pitfalls in the intraoperative examination of smears]

According to the Ste Anne hospital classification and grading system of oligodendrogliomas the presence of contrast enhancement on MRI and/or the presence of an histological endothelial hyperplasia are correlated with a pejorative prognosis (high grade or grade B). Surgical tumoral exerese and adjuvant chemo or radiotherapy are indicated. When clinical and radiological aspects are typical the extemporaneous diagnosis of oligodendroglioma on smear is usually easy (1). In case of atypical forms: unusual localization or cytological appearance, especially with a small cell hyperchromatic undifferenciated tumor few diagnostic hypothesismay be considered. Four cerebellar tumors are presented with relevant and differential cytological diagnostic criteria. A comparative study between clinical and radiological aspects of medulloblastoma, primitive lymphoma, undifferenciated small cell lung carcinoma, and grade B oligodendroglioma is presented.

So-called malignant and extra-ventricular neurocytomas: reality or wrong diagnosis? A critical review about two overdiagnosed cases

Central neurocytoma (CN) is described as a rare intra-ventricular benign neuronal tumor of the brain. Two primary tumors first diagnosed as malignant and extra-ventricular neurocytomas are reported here. Histologically, the tumor of the first patient, a forty-one-year-old man, consisted of monotonous cells with round nuclei, but no fibrillar background. The second tumor, in a nineteen-year-old girl, showed areas of moderately pleomorphic round cells, with numerous rosettes and ganglion cell differentiation, in an abundant fibrillary network. Both presented calcifications. Mitoses were more frequent in recurrences and spinal locations than in the primaries. All tumors stained strongly for synaptophysin, and GFAP was partly positive in the first case only. Patients received post-surgical radiotherapy and were still alive eight and six years, respectively, after initial surgery. The interpretation of atypical cases, such as ours is not easy: the diagnoses finally retained were oligodendroglioma in the first case and ganglioneuroblastoma in the second case. Furthermore, neurocytomas atypical either by their unusual topographical or histological presentation or by their poor prognosis, have been frequently entitled in this way on synaptophysin positivity. So, we were prompted to reassess the entity of CN, seventeen years after the first description, to re-appreciate the reality of anatomo-clinical variants and to discuss the value of synaptophysin positivity in these tumors. In conclusion, it seems preferable to individualize true classical CN, which has a favorable outcome, from so-called extra-ventricular, atypical and anaplastic, clinically malignant neurocytomas for which complementary treatment is required.

Modulated release of IdUrd from poly (D,L-lactide-co-glycolide) microspheres by addition of poly (D,L-lactide) oligomers

This paper reports the release characteristics of a radiosensitizer, 5-iodo-2'-deoxyuridine (IdUrd), from poly (D,L-lactide-co-glycolide) 50: 50 (PLGA) microparticles obtained by a phase separation technique. Poly (D,L-lactide) oligomers (D,L-PLA) were incorporated into the PLGA matrix in order to accelerate the overall drug release rate and regulate the triphasic release profile exhibited by the standard PLGA microparticles. For D,L-PLA (800), the burst effect was large and the IdUrd release was complete between 28 and 35 days. These results were attributed to rapid pore formation on the periphery of the microsphere in the early stages of incubation, due to hydrosolubility of the smallest oligomers (D,L-PLA (800)). In the case of D,L-PLA (1,100), drug release occurred over a six week period, the standard time course of conventional radiation therapy. The period during which the radiosensitizer was incorporated in human brain tumor cell nuclei after its entrapment in biodegradable microspheres was determined by using an organotypical tissue culture. The presence of radiosensitizer in the DNA of tumor cell nuclei was detected by immunohistochemical labelling of tumor fragments. IdUrd release from standard microspheres (7+/-0.5 weeks) was longer than from oligomer-containing batches. For D,L-PLA (800)-containing microspheres, the radiosensitizer was entirely released within 4. 5+/-0.5 weeks. The microspheres containing D,L-PLA (1,100) allowed an IdUrd release over a 5 to 6 week period. The ex vivo data were consistent with the in vitro findings in terms of release duration.