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A neurocytoma is a central nervous system tumor composed of small cells with features of neuronal differentiation; it typically occurs in the periventricular region, close to the septum pellucidum and the foramen of Monro. In this article, the authors report the case of a neurocytoma located in the cerebellum, which to their knowledge is the first reported case of its kind. The finding of a neurocytoma at a nonclassic location refutes the theory that this tumor has its origins in subependymal progenitor cells, unless an ectopic location of progenitor cells is invoked to explain the occurrence of a neurocytoma away from the ventricles. On the basis of this case, the authors suggest that neurocytomas should be added to the differential diagnosis of mass lesions in the supratentorial intraventricular regions as well as in the posterior fossa.

Recently cases of ganglioneurocytoma and cerebral neurocytoma, very rare variants of central neurocytoma, have been reported. The former is characterized by differentiation toward ganglion cells and the latter by extraventricular origin in the cerebrum, but their existence as distinct clinicopathological entities, is controversial. We report an unusual case of neurocytoma, which arose extraventricularly from the frontal lobe, formed a large cystic lesion and showed ganglioid differentiation, in a 11-year-old girl. Following subtotal tumor resection, she showed a satisfactory clinical course and no evidence of recurrence. This is a very rare case of central neurocytoma-like tumor outside the ventricular system and also of ganglioneurocytoma. This case may provide some insight into the tumorigenesis and widen the clinicopathological concept of neurocytoma.

Background: It has been suggested that the biologic behavior of central neurocytoma is indolent, although little is known regarding the role of radiation therapy and long term outcome. To clarify the role of radiation therapy and long term outcome, the authors retrospectively analyzed 15 cases of central neurocytoma., Methods: Clinical records and radiologic findings of 15 cases of central neurocytoma diagnosed at Seoul National University Hospital between January 1982 and February 1995 were carefully reviewed. The duration of follow-up was from 18-168 months (mean, 52 months); follow-up images were reviewed and the patient's Karnofsky performance scale (KPS) was assessed up to the time of last follow-up., Results: The age of the patients ranged from 15 to 60 years (mean, 25 years) and the male to female ratio was 11:4. Macroscopic total resection of the tumor was performed in seven patients, two of whom received fractionated radiation therapy. Subtotal removal of the tumor was performed in eight patients, five of whom received this same therapy. In 2 of the 5 patients who did not receive radiation therapy after macroscopic total resection, the tumors recurred 8 and 21 months after surgery, respectively; in contrast, recurrence was not detected in the 2 patients who received fractionated radiation therapy after macroscopic total resection. In all five patients who received fractionated radiation therapy after subtotal resection, the tumor shrank (n = 3) or disappeared (n = 2) during the postsurgical follow-up period ranging from 27-113 months; the tumor began to shrink from 6 months to 2 years after radiation. No change was found in the three patients who did not receive radiation therapy after subtotal resection. At the time of last follow-up, the KPS was greater than 90 in all patients except one who required assistance in his daily activities because of complications from radiation therapy., Conclusions: It is suggested that even if the biologic behavior of a central neurocytoma is benign, radiation therapy appears to have an effect on tumor control. However, it should be carefully decided whether to use radiation therapy for a residual tumor because radiation can cause delayed complications and the clinical course of subtotally resected patients who do not receive radiation therapy is extremely benign.

The proliferative potential of central neurocytomas was determined in a biopsy series of 36 cases and compared with clinical outcome. The mean size of the growth fraction, as determined by MIB-1 labeling index (MIB-1 LI) at first biopsy, was 2.8 +/- 2.5 with a range of 0.1 to 8.6%. Neurocytomas with an MIB-1 LI > 2% comprised 39% of cases and showed a close correlation with the presence of vascular proliferation (p = 0.0006). The Kaplan-Meier analysis showed a highly significant difference in disease-free survival between the 2 groups (p = 0.0068). Over an observation time of 150 months, there was a 22% relapse among patients with an MIB-1 LI less than 2% and a 63% chance of relapse among those with an MIB-1 LI greater than 2%. We propose the term "atypical central neurocytoma" for the latter subset, corresponding to WHO grade II.

The transcallosal approach has been widely used for tumors located near the midline of the anterior part of the lateral ventricle, while the transcortical approach is known to provide a wide surgical field in cases of hydrocephalus. However, it is not always easy to choose the appropriate approach in individual cases. The size of the visualized field obtained via the surgical approach is one of the most important factors determining the accessibility of the lesion. In this study, we investigated the difference in the sizes of the fields afforded by these two approaches on the basis of our clinical experience and simulation studies. We surgically treated intraventricular pathology located at the anterior part of the lateral ventricle in five patients with tumors and one with a cyst. Tumors with lateral extension of less than 20 mm were approached via the transcallosal route, and those with more than 20 mm of lateral extension via the transcortical route. In the simulation study, the size of the surgical field was measured through a 3-cm incision of either the cerebral cortex or the corpus callosum under various conditions of ventricular enlargement. Two patients treated via the transcortical approach underwent subtotal removal; one of them had a large bilaterally extending tumor measuring 50 mm in its greatest diameter, and the other had tumor involvement of the fornix. The other three tumors and the cyst were totally resected. While postoperative subcortical hematoma developed in two patients, one each treated via the transcortical and the transcallosal approach, no deficits remained at discharge. Since enucleation procedure was insufficient in patients with hard tumors, a wider surgical field than that in patients with soft tumors was considered necessary. When combined approaches are considered indispensable for a patient with a massive tumor, the transcortical approach may be indicated for priority of order to prevent bilaterally residual tumors. The simulation study disclosed that, in either approach, wider surgical field was obtained as the size of ventricle increased. However, the transcallosal approach afforded a wider field than did the transcortical approach not only in ventricules of normal size but also in mild hydrocephalus with cortical thickness of between 30 and 40 mm. The transcortical approach, on the other hand, produced a much wider field in more advanced hydrocephalus with a thickness of less than 30 mm. A wider surgical field can be obtained by certain tactics such as upward retraction of the incised corpus callosum, moving the cortical window, or oblique or transverse cortical incision.

Central neurocytoma is considered to be a benign intracranial neoplasm, but little is known about the biological behavior of this type of tumor. Proliferative activity of central neurocytoma was measured in 10 cases using MIB-1 staining for Ki-67 antigen. The MIB-1 staining value varied from < 0.1% to 5.6%, to indicating that some of these tumors have proliferative potential similar to that of anaplastic astrocytoma or malignant meningioma. The bromodeoxyuridine labeling index (BUdR LI, BrdU LI) was measured in 2 cases and the results correlated well with those of the MIB-1 analysis. Tumor volume doubling time (Td) measured in one case was 358 days which is similar to that of malignant meningioma. In one case, the MIB-1 value taken before and after 58 Gy of radiation treatment decreased markedly from 5.6% to 0.2%. The other 9 cases were also treated by radiation therapy (50-60 Gy) and no tumor recurrence was observed during follow-up periods ranging from 23 to 160 months. Another two patients with partially removed and 3 with subtotally removed tumors showing relatively high MIB-1 values might also have benefited from radiation therapy.

Tumors of central nervous system elements are uncommon in cystic teratomas and tend to be derived from glial or primitive neuroectodermal cells. We describe the case of a 23-year-old woman with a central neurocytoma arising in an otherwise mature cystic teratoma of the ovary. Histologically, the neurocytoma was composed of collections of oligodendroglioma like cells in a fibrillary matrix. Cytologically the tumor was identical in appearance to central neurocytomas occurring within the adult brain. It expressed synaptophysin and neuron-specific enolase, confirming its neuronal lineage, but not glial fibrillary acidic protein. The site of the tumor recapitulated the typical location of neurocytomas adjacent to the lateral ventricle in that in abutted onto an ependyma-lined cyst within the teratoma. The patient remains well and free of tumor 1 year after cystectomy, in keeping with favorable follow-up data for surgically excised central neurocytomas within the brain.

Central neurocytoma was first described in the literature in 1982 and has been noted to be a benign neuronal tumor usually located in the ventricular system. Of the more than 100 reported cases, only seven recurrences have been reported, all of which have been local. The authors report two cases of recurrent central neurocytoma that disseminated through the ventricular system with seeding to the spine, as evidenced by magnetic resonance images and positive cerebrospinal fluid cytology. The histological appearance of these two tumors was typical for the lesion and lacked evidence of malignant change. Central neurocytoma may not be as benign as previously thought, and the recognition of this more malignant behavior has implications for patient follow up and therapy.

In 1976 a patient underwent partial resection of an intraventricular tumor that showed central neurocytoma. No other tumor pattern was observed. In 1994 this patient underwent a second operation for removal of the tumor, at which time foci of tumor were diagnosed as central neurocytoma and ganglioglioma. This is the first reported case of differentiation of central neurocytoma into ganglioglioma, a sequence of events termed differentiating central neurocytoma.

The clinicopathological features of a series of neuronal and mixed neuronal and astrocytic neoplasms of the CNS are described. Patients were aged 5 to 63 years. Six cases were composed predominantly of small round cells with clear cytoplasm resembling central neurocytoma but lacked the characteristic intraventricular location of that tumor. The remaining five cases had similar neurocytomatous features associated with a benign astrocytic component. Ganglion cells and hyalinization vessels were observed in both groups. The growth fraction evaluated with monoclonal antibody Ki67Mib1 was low, ranging from 1 to 1.5%. Immunohistochemical detection of synaptophysin played a crucial role in identifying the neuronal nature of these neoplasms and was instrumental in distinguishing them from oligodendrogliomas, with which they are readily confused. The neuronal nature of the oligodendroglial-like cells was confirmed ultrastructurally in one case. The present cases, together with others reported previously, suggest that neoplasms of the CNS with "neurocytic" components are more frequent than generally assumed and expand the morphologic spectrum of neuronal and mixed neuronal-glial tumors. Except for one patient who died postoperatively, all patients were alive at follow-up ranging from 6 to 80 months.

A case of central neurocytoma that was confirmed with ultrastructural and immunohistochemical studies has been reported. Ultrastructurally, thin cytoplasmic processes of tumor cells showed differentiation into neuronal cells containing parallel bundles of microtubules and abortive synapses with dense-core vesicles and/or clear vesicles. It was frequently found that the clusters of tumor cell processes were close to or around the microvessels. Microvessels were composed of endothelial cells without fenestrations and had tight junctions in the endothelial clefts. Neurosecretory granules in thin cell processes appeared close to microvessels and may have been secreted around microvessels.

The authors report 8 cases of central neurocytoma with a minimum follow-up of 3 years. Five patients were males and 3 females with average age of 21 years. All patients underwent surgical removal of tumor, and radiotherapy was delivered to 2 of the 3 patients in whom removal had been partial. At an average follow-up of 5 years, all patients are alive and none of them has presented signs of recurrence or progression of the disease. Some typical clinical and histological features of this tumor are pointed out.

J. Hassoun and co-workers (1982) described two cases presenting intraventricular tumors of nervous origin, coined by them with the term "central neurocytoma" of the ground of electron microscopic data. As shown by the studies of other authors, central neurocytoma represents a separate morphological entity having light- and electron-microscopic and immunohistochemical characteristic of its own. In the recently published WHO classification of brain tumors (1993) central neurocytoma is entered as a tumor presenting new morphological patterns. Central neurocytoma occurs mainly in young persons, develops in the lateral and third ventricle, comparatively well differentiated from surrounding structures, rich in calcifications, disclosing proper relative specificity during CT scanning and MRI study. Light-microscopically this tumor bears resemblance to, and is erroneously diagnosed as oligodendroglioma or ependymoma. Proceeding from retrospective reassessment of two patients with intraventricular tumors and an additional observation, and on the ground of pertinent literature data, the morphological, clinical and nerve imaging characterization of central neurocytoma is outlined--a tumor met with in the daily routine practice, but usually erroneously interpreted.

A case of neurocytoma arising in the rostral pontine region of an 18 year old man is reported. The patient developed a right trochlear nerve palsy and was shown to have a well circumscribed, contrast enhancing mass on magnetic resonance imaging. The tumour was characterised histologically by a uniform population of medium sized round nuclei and slightly eosinophilic cytoplasm or occasional perinuclear halos, with delicate branching capillaries, patches of fibrillary matrix, and occasional perivascular pseudorosettes. Immunohistochemical studies demonstrated strong reactivity for synaptophysin in the fibrillary processes and cytoplasm of tumour cells. The present tumour is an exceptional case of neurocytoma arising in the pons.

The role of inflammatory reactions in brain tumors is still unclear. In particular, there is little information about the participation of the microglia/macrophage cell system. We therefore investigated 72 surgical biopsy samples of brain tumors (astrocytoma, glioblastoma, oligodendroglioma, ependymoma, medulloblastoma, cerebral lymphoma, gangliocytoma, neurocytoma and germinoma) and the brains of eight cases with malignant gliomas that came to autopsy, using immunohistochemical markers for the monocyte/macrophage lineage (Ki-M1P, HLA-DR, KP1, My4, My7, Ki-M1, Ki-M6, EBM 11). These markers allowed us to characterize four subtypes of the microglia/macrophage cell system: ramified microglia, ameboid microglia, perivascular microglia and brain macrophages. Among the different tumors, glioblastomas and anaplastic gliomas showed the largest number of mixed cell populations, which consisted of macro-phages and ramified and ameboid microglia. In glial tumors of low malignancy fewer, predominantly ameboid, microglia were found. Neuronal tumors showed only a mild increase of microglia. Cerebral lymphomas contained macrophages diffusely distributed within the tumor center, while activated microglia were prominent at the border zone and in the adjacent brain tissue. The autopsy cases were used to study the morphometric distribution of microglia/macrophages. There was a significant increase of microglia/macrophages within the tumor, but no differences were seen between central and peripheral tumor areas. The non-neoplastic gray and white matter contained more microglial cells than controls. We conclude that the distribution pattern of ameboid and ramified microglial cells and macrophages is distinct in most of the investigated tumor types, underlining the complex immunological function of the microglia/macrophage cell system.

The authors analyzed 13 central neurocytomas diagnosed at Seoul National University Hospital between January 1982 and December 1993 to clarify the proliferative potential and biological behavior of these tumors. The tumor was confined to the lateral and third ventricles in 12 cases and in one case extended from the posterior thalamus to the body and trigone area of the lateral ventricle. In all 13 cases, typical clinical and radiological findings were observed, and histological diagnosis was performed via craniotomy. The diagnosis was made using light microscopic examination, immunohistochemical staining for neuronal markers, and electron microscopic findings of neuronal differentiation. One patient died due to tumor progression with recurrence 26 months after subtotal removal plus radiation therapy. Another patient had a recurrence 18 months after total tumor removal. The remaining 11 patients are free of recurrent tumor after a follow-up period that ranged from 14 to 109 months (median 50 months). To predict the proliferative potential, immunoreactivity to proliferating cell nuclear antigen (PCNA), silver colloid staining for nucleolar organizing regions (AgNORs), and DNA flow cytometry were performed in 10 of the 13 cases. The proportion of PCNA-positive cells was less than 1% in all cases and the AgNORs score ranged from 1.11 to 2.0 (mean 1.67). The DNA flow cytometry revealed diploidy in all cases and the calculated proliferation index ranged from 5.1% to 9.6% (mean 7.8%). The one case of tumor recurrence, in which the authors performed the study of proliferative potential, and another case that demonstrated mild nuclear pleomorphism also showed low percentages of PCNA-positive cells, low AgNORs scores, and diploidy in DNA flow cytometry. It is suggested that most central neurocytomas follow a benign clinical course with low proliferative potential assessed by PCNA, AgNORs, and DNA flow cytometry; however, recurrence is possible within a relatively short time period.

A 30-year-old male presented with a large calcified intraventricular mass. The tumor was completely resected via the transventricular route. Light microscopy showed the tumor was composed of small round cells with perinuclear halo, typical of oligodendroglioma. Electron microscopy revealed marked neuronal differentiation, including neurosecretory granules, well-formed numerous synapses, and lipofuscin granules. The tumor was diagnosed as well-differentiated central neurocytoma.

This report describes an unusual neuronal tumor detected at the autopsy of a 17-year-old boy. The tumor showed multifocal parenchymal involvement with extensive leptomeningeal dissemination. The intraparenchymal lesions were small and located mainly in the subpial region of the cerebrum, cerebellum and spinal cord. Leptomeningeal dissemination was particularly pronounced at the base of the brain and around the spinal cord and presumably took place during the relatively long clinical course. The tumor was composed of small round cells and ganglion-cell-like cells. Only neuronal differentiation, as represented by immunostaining with antisynaptophysin antibody and the presence of dense-core vesicles in the cytoplasm, was evident in both types of cells. The small round cells appeared to exhibit the features of small, relatively mature neurons rather than those of neuroblasts. Moreover, our results suggested maturation from small round cells to ganglion-cell-like cells. The tumor appears to be related to gangliogliomas or dysembryoplastic neuroepithelial tumors, and we have chosen the term neurocytoma/gangliocytoma for the unusual lesion.

Central neurocytoma is a rare brain tumor composed of small round synaptophysin-positive cells, suggesting a neuronal origin of these tumor cells. Glial properties are inferred, however, from the observation that the tumor cells exhibit a strong morphological similarity to oligodendroglioma cells and show an astrocytic differentiation in vitro. To test for neuronal or glial physiological properties, we studied cultured neurocytoma cells derived from a surgical specimen from a 44-year-old man, employing the patch-clamp technique. Early primary cultures were composed of morphologically unique bi- or multipolar cells which were positive for synaptophysin and negative for the astrocyte marker glial fibrillary acidic protein. In the majority of these cells, whole-cell membrane current recordings revealed physiological properties of neurons, i.e., a high density of Na+ currents, the capacity to generate action potentials, and the expression of inotropic neurotransmitter receptors. Metabotropic neurotransmitter receptors could be demonstrated by Ca2+ imaging techniques. The remaining bi- or multipolar cells and almost all cells in later culture stages and in vitro passage lacked these neuronal properties and showed physiological features characteristic of glial cells. We conclude that the major population of neurocytoma cells shows physiological properties of neurons and that with time in culture this population is replaced by electrically passive cells.

Diagnostic dilemmas of biopsy specimens in the central nervous system (CNS) tumors are often the result of multiple factors, including fixation artifact, biopsy size, lack of immunohistochemical techniques to distinguish cell types, and unawareness of rare entities. Correct diagnosis and confirmation of diagnosis of primary CNS neoplasms is imperative and may require electron microscopic examination. In some instances, use of electron microscopy may be the only approach for accurate recognition of an entity. Although diagnostic electron microscopy is expensive and cost cutting is encouraged in today's practice of medicine, cost must be weighed against the consequences of even 1 patient developing CNS treatment-related necrosis or a radiation-induced neoplasm secondary to misdiagnosis of a benign entity. This study reviews the ultrastructural differences of three groups of diagnostically difficult CNS lesions: clear cell neoplasms (ependymoma, oligodendroglioma, central neurocytoma), rare entities containing astrocytes invested by a basal lamina (pleomorphic xanthoastrocytoma, the desmoplastic neuroepithelial tumors of infancy), and benign entities characterized by transitional cell forms (subependymoma, subependymal giant cell astrocytoma).

Background: Central neurocytomas are rare brain tumors recognized by their typical radiologic and histologic features. In general, a good prognosis is achieved by total removal. The histogenesis is still under debate, but a neuronal origin is widely assumed., Methods: This study presents the clinical and immunohistologic findings of five patients and the results of cell culture experiments of two patients with central neurocytoma treated surgically between 1983 and 1993., Results: The patient age at diagnosis ranged from 21 to 30 years (mean, 25 years). The male-to-female ration was 1:4. Raised intracranial pressure due to hydrocephalus was the main cause of the clinical manifestations. Total resection was achieved in two cases. Four patients received radiotherapy. One patient suffered a recurrence 1 year after surgery, requiring a second resection and radiotherapy. Follow-up studies took place between 1 and 10.5 years (mean, 7.1 years). To date, all patients are free of their tumors. Two patients suffered from permanent memory disturbances after surgery. Immunohistochemistry confirmed the neuronal nature of the tumors. Cell-culture studies, which have been carried out for the first time, demonstrated concomitant expression of neuronal (synaptophysin) and glial (GFAP) markers., Conclusion: Total removal is the therapy of choice. In tumor recurrence or limited surgery (e.g. due to severe affliction of the fornical structures), radiotherapy has shown to be efficacious. The cell-culture experiments give new insight on the histogenesis of central neurocytoma, indicating that the tumor arises from an undifferentiated precursor cell with the capacity of bipotential neuroglial differentiation.

We have identified two central neurocytomas which contained cells co-expressing glial fibrillary acidic protein and synaptophysin defined by double-label immunostaining. Dual-positive cells were mostly polygonal in shape and with a morphological appearance similar to that of reactive astrocytes. This distinct morphology could be used to distinguish cells expressing glial fibrillary acidic protein from cells with round and clear cytoplasm which did not express glial fibrillary acidic protein and which composed the majority of the tumor. Samples containing polygonal cells were selected for electron microscopy from toluidine blue-stained semithin sections. Ultrastructural findings were similar in both neurocytomas, with both being composed predominantly of round cells with clear cytoplasm corresponding to the clear cells identified by light microscopy. Dense-core vesicles and clear vesicles were frequently observed in the cell processes. Apart from these clear cells, polygonal cells with electron-dense cytoplasm were noted. Paralleling the result of double immunostaining, these polygonal cells contained both dense-core vesicles and intermediate, presumably glial filaments. Microtubules and lipofuscin granules were also observed. These results suggest that cells expressing glial fibrillary acidic protein in central neurocytoma include tumor cells with both neuronal and glial characteristics.

A case of central neurocytoma occurring in a 22-year-old man is presented. This tumor is generally considered to be benign in appearance, nonrecurrent, and amenable to surgical resection. However, this particular neurocytoma demonstrated anaplastic features, raising the issue of malignancy and the need for additional modes of treatment. Implicated factors and possible optimal treatment for this tumor are discussed.

To estimate proliferating activity of central neurocytoma, we measured kinetic rate constants and glucose metabolic rate (kinetic-rCMRGI) using dynamic positron emission tomography (PET), as well as autoradiographic rCMRG1 (arg-rCMRG1), in patients with histologically verified central neurocytoma. The subject included five patients, four males and one female, aged from 23 to 53 years with a mean age of 41 years old. All tumors were located in the lateral ventricle and two extended into the third ventricle through the forearm of Monro. Tumor lesion on the PET images was determined using CT or MRI, which was performed at levels equivalent to those for the PET scans. The kinetic rate constants of tracer transport from blood to brain (k1), reverse transport from brain to blood (k2), and phosphorylation (k3) were analyzed according to the three compartment 18F-fluorodeoxyglucose (FDG) model. For quantitative analysis, regions of interest (ROI) on PET images were delineated on the tumor and the contralateral gray matter. Tumor k1 and k2 values were similar to or higher than those of the contralateral gray matter, suggesting high permeability due to lack of blood-brain barrier. Tumor k3 value, an indicator of hexokinase activity, and kinetic-rCMRG1 were exceedingly lower in three of five patients. These three patients have been free from tumor recurrence or regrowth, postoperatively. The other two patients, tumor kinetic-rCMRG1 was similar to or higher than that of the contralateral gray matter. One patient suffered from tumor regrowth shortly after resection, and the other has been followed up postoperatively. Thus, k3 and kinetic-rCMRG1 are indicative parameters of proliferative activity in central neurocytoma.

Five cases of central neurocytoma, confirmed by immunohistochemical and electron microscopy studies, are reported and 127 cases from the literature are reviewed. Central neurocytomas are more frequent than previously thought, and will be diagnosed with increasing frequency in the future, if intraventricular tumors with histological aspect of oligodendroglioma or ependymoma will be routinely studied by immunohistochemistry and electron microscopy. The occurrence of an intraventricular tumor with a typical MR aspect in a young patient should suggest preoperatively the diagnosis of neurocytoma. The positivity for synaptophysin and neuron specific enolase, the negativity for neurofilament protein and glial fibrillary acid protein, and the finding of elements of neuronal differentiation on electron microscopy, are the main pathological features of these tumors. Complete removal of the tumor mass without radiotherapy is the treatment of choice. The prognosis is usually favorable without recurrence.

We report two cases of low-grade glioma in which multiple cellular components, including cells with dense-core granules consistent with "neurocytes," were identified on electron microscopic studies. The first patient was an apparently normal boy until the onset of seizures at age 10 months. Initially, the seizures improved with phenobarbital treatment, but good seizure control was never achieved. Computed tomographic scan at age 23 months showed a calcified, nonenhancing left parietal mass. This tumor was composed of sheets of cells with clear cytoplasm and round to oval nuclei. Mucinous intercellular material stained positively with periodic acid-Schiff, mucicarmine, and alcian blue stains. Foci of calcification were evident. The second patient was a 13-year-old boy with a left parasagittal parieto-occipital mass who presented with a 4-month history of seizures and declining school performance. The tumor was composed of sheets of astrocytes with dark, hyperchromatic, pleomorphic nuclei in a fibrillary and microcystic background. The tumor contained the pleomorphism seen in the adult variant of pilocytic astrocytoma, as well as the microcystic component seen in the juvenile variety. Ultrastructurally in both cases, there were occasional tumor cells having round to oval nuclei with moderate amounts of cytoplasm containing 150- to 250-nm-diameter dense-core granules. These cells were admixed with the majority of tumor cells, which in case 1 had the ultrastructural features of astrocytes and oligodendrocytes and in case 2 had features of protoplasmic or pilocytic astrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterised by distinctive clinicopathological features, the central neurocytoma (CN) is an uncommon and possibly under-recognised primary cerebral neuronal neoplasm. We present clinical and pathological details of seven patients with CN. Histological examination revealed a greater diversity of morphological appearances than is typically described in CN. No anaplastic features were identified. Cellular areas resembling both oligodendroglioma and ependymoma were present in all cases, but each tumour also contained stroma rich areas with hyalinised or aneurysmal vessels. Synaptophysin was expressed by all tumours and probably represents the immunohistochemical marker of choice for identifying CN. Distinguishing ultrastructural features included rounded cell bodies separated by numerous cell processes containing microtubules, pleomorphic neurosecretory granules and occasional synapses. Ki-67 immunostaining revealed a low cell proliferation index in each case. The distinction of CN from other pathological mimics can be reliably made using this multiparametric approach to diagnosis. The generally benign behaviour of CN is confirmed, though there was one patient death in the follow-up period of 10-122 months. Aggressive behaviour in this case was not associated with anaplastic histological features.

The central neurocytoma is a recently recognized benign intraventricular tumour of young adults. The authors report a unique case of a panventricular neurocytoma with extension to the interpeduncular and prepontique cisterns which developed in a 35-year-old woman with a 7-year history of headaches and amenorrhea. They review the different pathological and topographical patterns of previously published neurocytomas and discuss the histogenesis of this rare tumour.

A case of central neurocytoma is reported, presenting as a tumor of the occipital lobe, closely related to the ependyma of the occipital horn of the lateral ventricle but not actually invading it. This is a distinctly uncommon location, and only four tumors have been reported so far in a lobar position, without an intraventricular component. The case broadens our knowledge of this recently described tumor and gives an opportunity for discussion of the role of radiotherapy in its management, which currently remains controversial.

Central neurocytomas are uncommon intracranial neoplasms. More than one hundred cases are documentated in the literature. In this report we describe the clinical and histopathological features in two patients with intraventricular neurocytoma. As the light microscopic features of neurocytoma resemble with that of an oligodendroglioma, it is essential to differentiate these two tumours, using either ultrastructural or immunohistochemical techniques.

Crush preparation smears of a central neurocytoma revealed branching capillaries mixed with numerous single, polygonal cells showing well-defined, abundant, granular cytoplasm and eccentric, oval nuclei with finely granular chromatin and micronucleoli.

The case of a 33-year-old man is presented, who acutely developed disturbance of consciousness, symptoms of raised intracranial pressure and unilateral neurological signs. The underlying lesion was a hemorrhagic tumor located in the left lateral ventricle. On histological examination, the surgically resected mass proved to be a central neurocytoma, a benign neuroectodermal neoplasia. Difficulties in differential diagnosis by imaging technics and histopathology render this unusual lesion worth publishing. To the best of our knowledge, no similar report on this recently described rare entity has been published in Hungary.

Cultured human neurocytoma cells from two neurosurgical patients were analysed for their immunocytochemical staining patterns and growth characteristics. In both cases, the cells stained positive for glial acidic fibrillary protein (GFAP) within one day of tissue culture in medium, with and without fetal calf serum, whereas the histological tumor specimens were negative. Both cases contained cells concomitantly expressing GFAP and synaptophysin (SNP) in the primary cultures. Epidermal growth factor (EGF) was mitogenic for the cultured cells but not platelet derived growth factor alpha (PDGF AA) or nerve growth factor (NGF). It is concluded that the human neurocytomas may represent neoplasms of a pluripotent neuroglial cell which can provide an interesting model to study the determinants for human glial/neuronal differentiation in vitro.

Central neurocytoma is a rare intraventricular brain tumor that affects young adults and presents with nonspecific signs and symptoms. This distinct clinicopathological entity has a benign biological behavior with good prognosis following surgical intervention. Two cases of central neurocytoma are presented and the diagnosis and treatment discussed.

Two patients, 14 and 46 years of age, presented with diffuse, rapidly growing intracerebral tumors leading to death 6 1/2 and 9 1/2 months, respectively, after diagnosis. Histological examination showed sheets of moderate-sized tumor cells with clear cytoplasm and central nuclei interrupted by delicate arciform vasculature, an appearance distinctly different from that of neuroblastoma. Malignant features were present in the form of significant nuclear pleomorphism, numerous mitotic figures, and small foci of necrosis with some suggestion of adjacent pseudo-palisading in one case. Ultrastructural examination showed neuronal differentiation, including prominent neuritic processes, microtubules, dense-core neurosecretory-type granules, and synaptic bouton-like structures containing small, empty-appearing synaptic-type vesicles and synapse-like membrane "thickenings." Immunohistochemistry showed focal immunopositivity for synaptophysin, neurofilaments, neuron-specific enolase, and S100 protein. Immunoreactivity for glial fibrillary acidic protein (GFAP) was found at the margins of the tumors adjacent to some intratumoral blood vessels and in some tumor cells. These tumors seem to occupy a nosological "middle ground" between neuroblastoma and central neurocytoma.

Central neurocytoma is a neuronal neoplasm that occurs supratentorially in the lateral or third ventricles. The authors report the clinical, neuroradiological, and neuropathological features of two neurocytomas arising in the spinal cord of two men, aged 65 and 49 years. The patients presented with progressive neurological deficits referable to the cervical spinal cord. Magnetic resonance imaging revealed isodense intramedullary spinal cord tumors at the C3-4 level. Both tumors were initially misdiagnosed as gliomas. In Case 1 the correct diagnosis was made after electron microscopy revealed neuronal features. Immunostaining in Case 2 revealed that tumor cells were positive for synaptophysin and negative for glial fibrillary acidic protein, strongly indicating a neuronal tumor. It is suggested that this spinal cord neoplasm be included under the designation "central neurocytoma."

Central neurocytomas are a well-characterized group of neuronal tumors usually arising in the supratentorial ventricular cavities. We describe the anatomical and clinical study of seven of these neoplasms. Patients were in the first four decades of life, and tumors were usually located in one of the lateral ventricles. Surgical resection was subtotal in 6 cases. Light microscopic examination revealed predominantly benign lesions with morphological features similar to the so-called ependymoma of the foramen of Monro, of the oligodendrogliomas, and of the neuroblastomas. Immunohistochemistry and electron microscopy confirmed the diagnosis in each case, showing expression of neuron specific enolase and synaptophysin and containing microtubuli, neurosecretory granules, and presynaptic vesicles. In agreement with the literature, the authors stress the benign behaviour of most of these tumors and the need for systematic immunohistochemical and ultrastructural study. The actual roles of the extent of resection and of postoperative radiotherapy are still a matter of discussion.

We report a case of spinal cord neurocytoma in a 67-year-old man who had experienced a progressive numbness of the left foot during the previous 4 years. Magnetic resonance imaging showed a well-defined intramedullary tumor located at the T10-T11 level. The pathological examination revealed histological characteristics described in neurocytomas. The tumor cells showed a uniform small nucleus and clear or slightly eosinophilic cytoplasm with frequent perinuclear halos, resembling the picture of oligodendroglioma. Some tumor cells exhibited mature ganglion cell appearance. Electron microscopy showed cells with microtubules and dense-core vesicles in their cytoplasm and cytoplasmic process. Immunohistochemically, the majority of tumor cells expressed synaptophysin and neuron-specific enolase. We conclude that this tumor is an exceptional case of neurocytoma located in the spinal cord, and consider that the term neurocytoma can be applied to tumors with neuronal differentiation intermediate between neuroblastoma and ganglioneuroma, even if arising in CNS outside of the intracranial ventricular system.

Central neurocytoma is a rare benign tumour of neuronal origin that has only recently been described. The majority of previously reported cases have originated from the septum pellucidum and the walls of the lateral ventricles. We describe a case of central neurocytoma arising from the thalamus. This site of origin has not been previously described. A review of the literature and discussion of the management follow.

A 30-year-old female presented with a central neurocytoma manifesting as positional headache. Magnetic resonance imaging showed a large calcified mass in the right lateral ventricle. The tumor was completely removed surgically. Light microscopy showed a linear arrangement of well-defined cells (beaded-string pattern) containing small round nuclei with abundant perikarya. A perinuclear halo reminiscent of oligodendroglioma was prominent in some cell groups. The tumor was entirely amitotic and free of atypia. Large, plump spheroid bodies lacking nuclei but containing coarse brown pigments were present among the tumor cells. The tumor cells were immunoreactive to neuron-specific enolase and synaptophysin but not glial fibrillary acidic protein or neurofilament. The ultrastructure of the tumor cells included abundant spheroid bodies containing secretory granules around neurons, indicating a dystrophic or aborted process of neuronal differentiation rather than a completely-differentiated central neurocytoma.

The central neurocytoma is a supratentorial, often calcified brain tumour affecting young adults and is typically located in the lateral ventricles in the region of the foramen of Monro. Clinically, the tumour causes signs of increased intracranial pressure, visual and mental disturbances and, occasionally, pyramidal or endocrine symptoms. By light microscopy, the tumour is composed of small round cells in a delicate fibrillary matrix. Tumour cells consistently show features of neuronal differentiation by electron microscopy (synapses, dense-core vesicles, presynaptic clear vesicles, specialized synaptic junctions) and immunoreactivity for synaptophysin and other neuronal marker proteins. The tumour can be totally removed in nearly half of the cases. After incomplete surgical resection neurocytomas may recur but because of their low proliferation potential, radio- or chemotherapy are not generally recommended. Postoperative recurrence-free survival times of up to 19 years have been reported. Neurocytomas constitute nearly one half of supratentorial intraventricular tumours in adults but amount to less than 1% of all tumours of the central nervous system and its coverings.

Two cases of central neurocytoma are presented. This is a rare CNS tumour affecting, predominantly, young individuals. There is enough evidence in the literature now to distinguish this entity clinically, radiologically and histologically. Much less is known about the management of patients with this tumour, because most of the reports are in pathological literature. Using our two cases and reviewing the available literature, we are endeavouring to shed light on the clinical aspects and management of central neurocytoma. In particular, we attempted to evaluate the role of surgical excision and radiation therapy in the management of this tumour.