Intraventricular neurocytoma: clinicopathological features of six cases

Central neurocytoma: clinical features of 8 cases

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.

Central neurocytoma occurring in the thalamus: CT and MRI findings

A case of central neurocytoma occurring in the thalamus, confirmed by electron microscopy and immunohistochemistry, is reported. Computed tomography demonstrated a hypodense mass with an irregular margin arising from the right thalamus, extending into the lateral ventricle and crossing the midline. It contained areas of calcification and showed slight enhancement after contrast injection. On magnetic resonance imaging (MRI) scan, the tumour was hypointense to the brain in T1-weighted images and was heterogeneously hyperintense to the brain in T2-weighted images.

Intraventricular neurocytoma

Intraventricular neurocytoma is a rare cerebral tumour which is usually associated with a good prognosis. It has imaging features which help differentiate it from other cerebral tumours. We report three cases including the first to originate from the pineal gland. The report emphasizes the radiological appearance and reviews the literature.

Central neurocytoma: proliferative potential and biological behavior

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.

Central neurocytoma: clinical, immunohistologic, and biologic findings of a human neuroglial progenitor tumor

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.

Blood flow and metabolism of central neurocytoma: a positron emission tomography study

BACKGROUND

New World Health Organization classifications have categorized central neurocytomas as neuronal tumors. The differential diagnosis between central neurocytomas and other tumors is important for selection of the optimal therapy modality for the management of intraventricular tumors. To characterize the pathophysiology and proliferating activity of central neurocytoma accurately, cerebral blood flow and metabolism in five patients with central neurocytoma were studied using positron emission tomography (PET).

METHODS

Tracers used for the present study included C15O2, C15O, 15O2, and 18F-fluorodeoxyglucose (FDG). Regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), cerebral metabolic rate of oxygen (rCMRO2), and cerebral metabolic rate of glucose (rCMRGl) were quantitatively analyzed in tumor lesions and the contralateral gray matter. Four patients with central neurocytoma underwent a complete PET study, including all circulatory and metabolic parameters; one patient was studied with 11C-methyl-L-methionine and FDG tracers.

RESULTS

Tumor rCBF and rCBV were higher than comparable values in the contralateral gray matter in three of four patients. This high level of perfusion corresponds to angiographic findings that show intense tumor staining in tumors fed by perforated arteries. Tumor rOEF and rCMRO2 were significantly lower than corresponding values in the gray matter (rOEF, P < 0.01; rCMRO2, P < 0.05 by Student's t test). Tumor rCMRGl ranged from 2.68 to 6.26 mg/100 ml/minutes and did not exceed contralateral gray matter values in any of the five patients. Tumor rCMRGl was significantly lower (P < 0.02) than the gray matter rCMRGl. One tumor exhibited a relatively high value of rCMRGl (comparable to gray matter rCMRGl), and increased in size 4 months after partial resection. No other tumors appeared during postoperative follow-up periods that ranged from 4 to 135 months.

CONCLUSIONS

Circulation and metabolism parameters measured by PET offer insight into the biologic characteristics of central neurocytoma. Tumor rCMRGl may be an indicator of the proliferating activity in central neurocytoma.

Central neurocytoma: clinico-pathological study of 5 cases and review of the literature

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.

Glioneurocytoma: tumor with glial and neuronal differentiation

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)

Central neurocytoma with hemorrhagic onset

A case of central neurocytoma with spontaneous intraventricular hemorrhage is reported. A 23-year-old man, 2 years after experiencing intraventricular hemorrhage, developed severe headaches. The magnetic resonance image showed a mixed intense mass in the lateral ventricle with associated hydrocephalus. The tumor mass was totally removed. The tumor was histologically diagnosed as central neurocytoma. Review of the computed tomography taken 2 years ago showed not only the hemorrhage but also a mass in the left lateral ventricle. This emphasizes that central neurocytoma should be considered in the differential diagnosis of patients with either intraventricular hemorrhage or hemorrhagic tumor.

Central neurocytoma. A clinicopathological, immunohistochemical and ultrastructural study of 7 cases

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.

Central neurocytoma without intraventricular extension

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.

Human neurocytoma cells in culture show characteristics of astroglial differentiation

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.

Malignant neurocytic tumor

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.

Review article: computed tomography and magnetic resonance in the diagnosis of intraventricular cerebral masses

We describe a series of 60 cases of patients with masses arising within the cerebral ventricles. The site and relative frequency is noted for each histological type. The differential diagnosis depends on patient age and sex, site, morphology and number of masses, presence and type of hydrocephalus and the characteristics of the mass on computed tomography (CT) and magnetic resonance (MR) images. A review of the literature has been performed and this information collated with our own experience to give detailed descriptions of the typical features of each intraventricular mass. Attention is drawn to intraventricular neurocytoma, a recently described tumour that may be mistaken histologically for intraventricular oligodendroglioma or ependymoma. A comparison is made of the value of CT and MR in the diagnosis of intraventricular masses.

Central neurocytoma of thalamic origin

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.

Central nervous system gangliogliomas. Part 1: Pathology

Histopathological features that suggest the diagnosis of ganglioglioma require, in most cases, confirmation by special stains to distinguish these tumors from other gliomas. For this purpose, immunostaining for synaptophysin, which has previously been shown to selectively label the cell surface of neoplastic ganglion cells, was used to retrospectively examine glioma tumor specimens. Sixty-three cases of ganglioglioma were identified. The files of the Division of Neuropathology of New York University Medical Center contained 45 tumors that had been diagnosed as ganglioglioma, of which 42 were verified by synaptophysin; three cases were reclassified, two as astrocytomas and one as a gangliocytic paraganglioma. Thus, a tumor identified as ganglioglioma based on other criteria was likely to be a ganglioglioma. The other 21 cases of gangliogliomas were originally diagnosed as astrocytoma or mixed glioma, but were shown by synaptophysin staining to be gangliogliomas. In some cases the ultimate diagnosis was obtained after radical surgery provided relatively abundant amounts of tissue, thereby limiting sampling errors, in contrast to the biopsies from which the original diagnoses were made. Histopathological review of these cases demonstrated that four features represent important clues to the correct diagnosis: 1) clusters of large cells potentially representing neurons (without such cells the tumor cannot be classified as a ganglioglioma); 2) no perineuronal clustering of the glial cells around the alleged neoplastic neurons; 3) fibrosis (desmoplasia); and 4) calcification. Binucleate neurons, previously suggested to be common in gangliogliomas, were not frequently found in this series, and lymphocytic infiltrates, while common, are so often found in other tumors that they gave no specific hint that any single neoplasm was a ganglioglioma. The glial elements were astrocytic in all cases, except that one tumor also had oligodendroglial and ependymal patterns. Four tumors also had small mature neurons, as seen in neurocytomas. Cells from one tumor were successfully grown in short-term tissue culture; the culture contained large dividing neurons with synaptophysin immunoreactivity as well as smaller dividing cells, demonstrating that the neuronal cells are a proliferating element in gangliogliomas.

Radiation therapy of well-differentiated neuroblastoma and central neurocytoma

BACKGROUND

Central neurocytoma is a rare intraventricular tumor with prominent neuronal differentiation. Although reported cases of this disease are increasing, the clinical benefit of radiation therapy remains unclear.

METHODS

From 1979 to 1990, two patients with central neurocytoma and five with well-differentiated neuroblastomas received radiation therapy. Five were men and two were women; the age at onset ranged from 20 to 37 years (mean age, 25.6 years). The follow-up period ranged from 14 to 134 months (median, 68 months). The initial histologic diagnosis was oligodendroglioma in five, ependymoma in one, and suspected central neurocytoma in one. Electron microscopic examination showed numerous neuronal processes containing microtubules and membrane-bound neurosecretory granules. Well-formed synaptic junctions were observed in the two cases of central neurocytoma. All patients underwent partial or subtotal tumor resection before radiation therapy (partial resection in three and subtotal resection in four). Three patients received radiation therapy locally, up to 50-60 Gy. Four cases were treated with a combination of whole brain irradiation (32-40 Gy) and local irradiation (20-32 Gy).

RESULTS

Treatment results were quite favorable, and all patients are alive and well without evidence of recurrence. Computed tomography studies showed that bulky residual tumors disappeared from several months to 1 year after the completion of radiation therapy. In a patient who had surgery again, significant vacuolar degeneration was observed by light microscopic examination.

CONCLUSIONS

A high level of radiosensitivity was confirmed, but additional data are required to clarify the clinical benefit of radiation therapy.

Central neurocytoma: a synopsis of clinical and histological features

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.

Immunocytochemical detection of calcineurin and microtubule-associated protein 2 in central neurocytoma

An immunohistochemical study was carried out on four cases of central neurocytoma, which had characteristic clinicopathological features including ultrastructural findings. Specific antibodies to calcineurin (CaN), microtubule-associated protein 2 (MAP2) and synaptophysin (SYP) were used. All tumor tissues examined showed specific immunoreactivity for CaN and MAP2. Immunolabelling of both molecules revealed that they were mainly localized in the perikarya and proximal processes of the tumor cells. SYP immunoreactivity was found in three of the four cases. SYP immunoreaction products were predominantly seen in the tumor cell processes, while the perikarya were weakly or moderately positive for SYP. The data suggest that CaN and MAP2, together with SYP, can be useful tools for identifying and characterizing of the central neurocytoma.

Central neurocytoma: report of 2 cases and literature review

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.

Central neurocytoma presenting with gigantism: case report

We report a case of central neurocytoma presenting with gigantism. The patient was a 19-year-old man with a 2-year history of rapid growth. Computed tomography revealed a round, slightly enhancing calcified tumor in the septal region. This lesion was resected, and postoperative radiotherapy was given. The preoperative serum growth hormone level was 20.7 ng/mL, and postoperatively this fell to 0.9 ng/mL. Pituitary dysfunction was not noted either before or after the operation. A low level of production of growth hormone releasing factor was detected when tumor cells obtained during surgery were cultured.

Cerebral neurocytoma. A new subset of benign neuronal tumors of the cerebrum

Three cases of patients with unusual neuronal tumors in the cerebral hemisphere are reported. All were associated with long-standing epileptic seizures. Computed tomography disclosed low-density lesions without contrast enhancement, which were interpreted as either arachnoid cysts or a cerebral infarction at initial diagnosis. Magnetic resonance imaging scans, however, revealed the lesions to be solid tumors. At surgery, the tumors were found to be relatively well demarcated, soft, and gelatinous. Histologically, all tumors were composed of small uniform stellate cells, which proliferated in a loose myxoid fibrillary matrix and resembled either oligodendroglial or astrocytic tumors. Ultrastructurally, however, all tumors showed neuronal differentiation, including numerous clear and occasional dense-core vesicles, microtubules, and a number of synapses. A review of the literature uncovered no other such cases, and therefore it was decided to classify these tumors as a distinct group of benign neuronal tumors, designated as "cerebral" neurocytoma compared with "intraventricular" neurocytoma. Related nosologic problems of neuronal tumors of the central nervous system and their possible histogenesis are also discussed.

Periventricular neurocytoma: a pathological entity

Three cases of periventricular neurocytomas are presented. All patients had a large but well-circumscribed, hyperdense tumor with insignificant contrast enhancement in the lateral and third ventricle, causing hydrocephalus. Calcification was present in one patient. Angiography revealed a blush tumor enhancement in two cases. Surgical removal was complete in two patients and incomplete in one. Light microscopy showed a cell pattern that resembled either ependymoma or oligodendroglioma. However, in all cases the tumor was confirmed to be a neurocytoma by immunocytochemical analysis that showed reactivity for synaptophysin and/or neuron-specific enolase in a high percentage of neoplastic cells. With respect to the literature it is concluded that neurocytomas represent an individual pathological entity of supratentorial midline tumors. Complete surgical removal without irradiation is the recommended treatment.

Hypothalamic neurocytoma with vasopressin immunoreactivity: Immunohistochemical and ultrastructural observations

Hypothalamic tumors of neuronal derivation are rare. We describe the case of a 55-year-old woman with visual disturbances who was found by magnetic resonance imaging (MRI) to have a sellar and suprasellar tumor. She underwent subtotal surgical resection by a transsphe-noidal approach. By light microscopy the tumor displayed a uniform population of short spindle cells with round to oval nuclei, separated by an abundant fibrillary stroma containing axonal processes as shown by the Bodian stain. The neoplastic cells were immunoreactive for neuron-specific enolase (NSE), synaptophysin, and vasopressin, and nonimmunoreactive for glial fibrillary acidic protein (GFAP), vasoactive intestinal peptide (VIP), bombesin, chromogranin, neurofilament, cytokeratins (high and low molecular weight), vimentin, S100 protein, somatostatin, β-endorphin, galactosamine, growth hormone-releasing hormone (GRH), neurophysin, serotonin, adrenaline and noradrenaline, and corticotropin-releasing hormone (CRH). Ultrastructural features included an abundance of neurosecretory granules within neurites and perinuclear cytoplasm. Synapses and glial stroma were not demonstrable. The term hypothalamic neurocytoma delineates this neuronal tumor with distinctive histologic, immunohistochemical, and ultrastructural features. The identification of vasopressin within the tumor provides evidence of neuroendocrine function.

Intraventricular neurocytoma: clinicopathological analysis of seven cases

A retrospective analysis of seven patients with intraventricular neurocytoma is presented. Patient age at diagnosis ranged from 15 to 38 years (mean 24.6 years) and the male:female ratio was 6:1. Raised intracranial pressure due to hydrocephalus was the main cause of the clinical manifestations. An isodense mass with multiple intratumoral cysts and homogeneous contrast enhancement was the characteristic computerized tomography finding. The lesions commonly involved the lateral ventricle with or without extension to the third ventricle. Cerebral angiography showed homogeneous vascular staining in five patients. Magnetic resonance images revealed a mass isointense with the cerebral cortex on both T1- and T2-weighted images. Gadolinium-diethylenetriaminepenta-acetic acid-enhanced images showed homogeneous enhancement. Total removal of the tumor was possible in four patients. Pathologically, six cases were initially diagnosed as oligodendroglioma and the remaining case as ependymoma. However, immunohistochemical studies demonstrated strong positivity for neuron-specific enolase in all seven cases and for synaptophysin in five cases. On electron microscopy, three cases showed well-defined neurosecretory granules and 10-nm microtubules in their cytoplasm and cytoplasmic processes. One patient developed a recurrent tumor 18 months after surgery. The remaining six patients are free of recurrent tumors at 2 to 62 months after surgery. It is suggested that neurocytoma must be included in the differential diagnosis of intraventricular lesions, and that electron microscopic and immunohistochemical studies should be undertaken.

Central neurocytoma: histopathological variants and therapeutic approaches

The central neurocytoma has recently been added to the differential diagnosis of intraventricular tumors. Histopathologically, this tumor is characterized by a uniform neoplastic cell population with features of neuronal differentiation. Central neurocytomas occur in young adults, develop in the area of the foramen of Monro, and are usually associated with the septum pellucidum. Initial reports appeared to indicate that these tumors are benign lesions with a favorable postoperative prognosis. The authors present clinical and neuropathological findings in a series of eight patients with central neurocytoma. An anterior transcallosal microneurosurgical approach yielded good outcomes. Postoperative radiation therapy was restricted to two patients with a malignant variant of central neurocytoma and one patient with a recurrent tumor. Observations of anaplastic variants of this neoplasm in two cases and local tumor recurrences in three indicate that the biological behavior and postoperative prognosis of central neurocytoma may not always be as favorable as previously assumed.

Central neurocytoma: immunohistochemical and ultrastructural study

Eight cases of central neurocytomas were studied by immunohistochemistry and electron microscopy. Seven tumors were located in the lateral ventricles and one in the subependymal region. All but one patient had a favorable postoperative course. The tumors were composed of small uniform cells possessing amitotic round nuclei with frequent perinuclear halos, a few Homer Wright rosettes and no ganglion cells; an appearance resembling that of oligodendroglioma. Immunohistochemical studies disclosed neuron-specific enolase and Leu-7 positivity in all tumors, S-100 protein-positive cells were found in six, while glial fibrillary acidic protein--and vimentin-positive cells were confined to the blood vessels. Myelin basic protein as well as neurofilament were not detected in the tumors. Synaptophysin-positive areas were seen in one tumor. Ultrastructural examination showed distinctive neuronal tumor cells which had a cytoplasm with sparse dense-core vesicles and thin cell processes containing parallel microtubules. They were classified into three different types of tumor cells according to the extent of differentiation. The most consistent finding for histological diagnosis was the presence of typical or abortive synapses with clear and dense-core vesicles. Additionally, synaptophysin may be a specific marker for some central neurocytomas.

Neuroradiology of central neurocytoma

Central neurocytomas (CN) are rare, usually benign cerebral intraventricular neuroepithelial tumors, which occur in adult patients. Retrospective evaluation of the CT- and MRI-findings in eight cases as well as review of the cases reported in the literature showed that CN usually presents as a primarily slightly hyperdense and/or hyperintense mass within the body of the lateral ventricle with moderate contrast enhancement. The majority of tumors contain both multiple small cysts and calcifications and exhibit a characteristic broad based attachment to the superolateral ventricular wall. We conclude that these criteria appear to be reliable to exclude other intraventricular tumors such as astrocytoma, giant cell astrocytoma, ependymoma, subependymoma, intraventricular oligodendroglioma and meningioma. Preoperative diagnosis of CN may prove of value for planning therapy, because this tumor type seems to have a better prognosis than other intraventricular tumors.

Intraventricular neurocytoma, a recently recognized pathological entity: report of two cases and review of the literature

Neurocytoma has only recently been recognized as a distinct pathological entity. Previously a rare tumor, it is now being recognized with increasing frequency. It typically presents in an intraventricular location in young adults. Many neurocytomas were originally diagnosed by light microscopy as oligodendrogliomas. More recently they have been shown to have ultrastructural and immunohistochemical features of neuronal differentiation. This paper presents two cases of intraventricular neurocytomas and reviews the recent literature.

Primary cerebral ganglioneurocytoma in an adult

A case of an unusual cerebral neuronal tumor in a 37-year-old woman is described. A clearly marginated tumor, which was found to occupy the septum pellucidum, genu of the corpus callosum, and right frontal lobe, was composed of ganglionic and small round cells. These two populations of neoplastic cells were both interpreted as being in the advanced stages of neuronal maturation, and the authors thus designated this tumor as a "ganglioneurocytoma." Related nosologic problems on central neuronal tumors and their possible histogenesis are also discussed.

Patterns of differentiation in central neurocytoma. An immunohistochemical study of eleven biopsies

Central neurocytoma has been characterised by its intraventricular localisation, predominant occurrence in young adults, oligodendroglioma-like histology, benign course and ultrastructural evidence for neuronal differentiation. Eleven intraventricular central neurocytomas were studied histopathologically, employing cell type-specific immunocytochemical markers and electron microscopic analysis. In the past, these lesions have caused diagnostic problems since central neurocytomas share basic histopathological features with other periventricular neoplasms. Accordingly, several tumours of this series had previously been classified as ependymomas of the foramen of Monro or oligodendrogliomas. Although generally regarded as benign lesions, two central neurocytomas of this series showed histopathological evidence of anaplasia, with focal necrosis, mitotic activity and vascular proliferation. All central neurocytomas exhibited immunoreactivity for neuron-specific enolase and synaptophysin, indicating consistent neuronal differentiation. Three tumours were studied by electron microscopy and contained synaptic vesicles, neuritic processes and neurosecretory granules. In addition, one tumour contained ganglioid cells and this was associated with focal immunoreactivity for neurofilament protein, suggesting that some central neurocytomas may, at least focally, continue to differentiate towards the formation of mature neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary cerebral neuroblastoma (neurocytoma) in adults

We report a case of a third ventricular neuroblastoma (neurocytoma) in a 66 year old man. A stereotactic needly biopsy was performed to obtain a tissue diagnosis and was followed by total resection. We elected not to give radiation or chemotherapy and to follow the patient closely with serial CT scans. Presently, 48 months postoperatively, the patient is free of tumor by head CT scan and able to live independently. We reviewed the literature of primary cerebral neuroblastomas/neurocytomas occurring in adults (greater than or equal to 15 years of age) and found 32 cases. Our patient is the oldest of this group with a mean age of 32 +/- 14 years (S.D.). The location of the 33 neoplasms was intraventricular in 17 cases (52%) and intraparenchymal in 16 cases. The male to female ratio was 2:1. Of the 17 patients having a minimal follow-up period of 5 months (mean 51 months), five developed recurrences after 5 to 144 months (mean 50 months) compared to 12 patients without recurrence after a 6- to 72-month follow-up period (mean 52 months). Recurrences occurred statistically significantly more often in parenchymal neuroblastomas/neurocytomas than in intraventricular tumor locations.