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A rare case of extraventricular neurocytoma (EVN) arising from the VIIIth cranial nerve in a 34-year-old woman is reported. The patient had a 20-year history of hearing loss and facial palsy. Computed tomography showed a 3-cm enhancing lesion in the left cerebellopontine angle (CPA). At operation, the tumor was seen to originate from the cochlear and vestibular nerves. The tumor was subtotally resected. Histologically, the tumor consisted of uniform cells with oval to round nuclei and scant cytoplasm. Immunohistochemically, the tumor cells were positive for synaptophysin, but negative for glial fibrillary acid protein and S-100 protein. The Ki-67 labeling index was 0%. Twelve years after the operation, magnetic resonance imaging (MRI) showed tumor recurrence at the left CPA. The tumor was subtotally resected, and radiation therapy was given. Histologically, the tumor consisted of round cells with mild atypia and one mitosis/20 high-power fields (HPF). Immunohistochemically, tumor cells showed the same findings as the first operation sample, except for the Ki-67 labeling index (3%). Twelve years after the second operation, MRI showed a second tumor recurrence at the left CPA and surroundings of the brain stem. The tumor was subtotally resected. Histologically, the tumor consisted of anaplastic short spindle cells and five mitoses/10 HPF. The immunohistochemical findings were almost the same as the earlier operation samples. However, the Ki-67 labeling index was 20%. In addition, tumor cells from the third specimen were more strongly and more diffusely positive for GAB1 (growth factor receptor-bound protein 2-associated binding protein 1) compared to those of the earlier specimens. Electron microscopy showed the presence of numerous cell processes with a dense core and clear vesicles and microtubules. GAB1 immunostaining also indicated that malignant progression might be associated with the sonic hedgehog signaling pathways. To the best of our knowledge, this is the first report of an EVN arising from the VIIIth cranial nerve with malignant progression.

Aim. Mesial temporal extraventricular neurocytoma (mtEVN) is a rare cause of refractory complex focal seizures. The characteristics of this clinical entity are discussed in this article. Methods. We report two cases of mtEVN and review the related literature, with particular emphasis on radiological characteristics, clinical features, and operative techniques. Results. After successful surgery, our two cases of mtEVN achieved excellent outcome. Including the cases presented here, a total of three cases of mtEVNs and 11 of neocortical temporal extraventricular neurocytoma (ntEVNs) are reported in the literature. mtEVNs are distinct from ntEVNs with regards to demographics, aetiology, radiological features, and operative techniques. Conclusion. mtEVNs and ntEVNs exhibit distinguishing features. Under electrocorticographic monitoring, tailored resection of the neocortical epileptogenic focus, as well as the entire tumour and mesial temporal structures, can yield excellent outcome and satisfactory seizure control.

With respect to localization, oligodendrogliomas are characterized by a marked preponderance of the cerebral hemispheres. Outside these typical sites, any tumor histopathologically reminiscent of oligodendroglioma a priori is likely to represent one of its morphological mimics, including clear cell ependymoma, neurocytoma, pilocytic astrocytoma or glioneuronal tumors. This is particularly relevant as several of the latter are in principle curable by surgery. Among extrahemispherical sites, bona fide oligodendroglioma - as characterized by loss of heterozygosity (LOH) of chromosome arms 1p and 19q - so far has not been documented to occur in the brain stem. Here, we report the case of a 55-year-old female patient with an anaplastic oligodendroglioma (WHO grade III) of the brain stem and cerebellum diagnosed by stereotactic biopsy and featuring combined LOH of 1p and 19q. A morphological peculiarity was a population of interspersed tumor giant cells, a phenomenon that has been referred to as polymorphous oligodendroglioma. Our findings confirm the notion that - although very infrequently - true oligodendrogliomas do occur in the infratentorial compartment.

Background In humans, central neurocytomas are rare and typically benign intracranial tumors found within the lateral ventricles, although extraventricular variants have been reported. Intracranial central neurocytomas have not been previously recognized in domestic animals. Objectives To describe the clinicopathologic features of canine intracranial central neurocytomas. Animals Two dogs with spontaneous intracranial and intraventricular neoplasms. Results Both dogs experienced seizures, rapid neurological deterioration, and death from tumor-associated complications within 5 days of the onset of clinical signs, and had neoplastic masses within the lateral ventricles. A brain MRI was performed in 1 dog, which revealed a T1-isointense, heterogeneously T2 and FLAIR hyperintense, and markedly and heterogeneously contrast-enhancing mass lesions within both lateral ventricles. Histologically, the neoplasms resembled oligodendrogliomas. The diagnosis of central neurocytoma was supported by documenting expression of multiple neuronal markers, including neuron-specific enolase, synaptophysin, neural-cell adhesion molecule, and neuronal nuclear antigen within the tumors, and ultrastructural evidence of neuronal differentiation of neoplastic cells. Conclusions and Clinical Importance Central neurocytoma should be a differential diagnosis for dogs with intraventricular brain masses. Morphologic differentiation of central neurocytoma from other intraventricular neoplasms, such as ependymoma or oligdendroglioma, can be difficult, and definitive diagnosis often requires immunohistochemical or ultrastructural confirmation of the neural origin of the neoplasm.

Reported herein is a case of central neurocytoma with differentiation toward ganglion cells, considered to be a typical case of ganglioneurocytoma. Tumor cells of various degree of differentiation toward ganglion cells were intermingled with typical neurocytoma cells in a fibrillary background, with transition of tumor cells from typical neurocytoma cells to differentiated ganglion cells evident throughout the tumor. The tumor cell nuclei were positive for NeuN. Fine granular positivity for synaptophysin was seen in the cytoplasm of the tumor cells, and background fibrils and the cytoplasm of some ganglioid cells were positive for neurofilament. Several cases of central neurocytoma with ganglioid cells have been reported, with some diagnosed as ganglioneurocytoma. However, histopathological details and persuasive figures have been lacking. It is considered that the diagnosis of ganglioneurocytoma should be applied to tumors displaying the following characteristics: (i) clinical aspects such as location, demarcation and growth rate consistent with neurocytoma; (ii) transition between neurocytoma cells and ganglion cells; and (iii) ganglioid cells distributed throughout the tumors.

BACKGROUND. Little is known about long-term results of gamma knife (GK) stereotactic radiosurgery (SRS) as a primary or a secondary postoperative therapy for central neurocytomas (CNs). The authors retrospectively reviewed long-term outcomes of 13 patients with CN treated with GK SRS. METHODS. Thirteen patients were treated with GK SRS as a primary (6 patients) or a secondary postoperative therapy (7 patients). Follow-up clinical status and brain magnetic resonance imaging (MRI) were thoroughly analyzed. The functional status of patients was assessed with the Karnofsky Performance Scale during follow-up. RESULTS. The median follow-up period for clinical status and imaging studies was 61 months (range, 6 months to 96 months). Tumors decreased in 5 patients who received GK SRS as a primary treatment. However, the tumor recurred in 2 patients treated with a secondary GK SRS after surgery from the residual tumor bed that was not covered by the GK SRS. Parenchymal changes and secondary malignancies were not found in follow-up MRIs of all 13 patients. The Karnofsky Performance Scale score of all patients, except for 1 patient who suffered from an unrelated anteriorly communicating arterial aneurysmal rupture, did not change after GK SRS. CONCLUSIONS. GK SRS may be useful as a primary or a secondary postoperative therapy for the treatment of CN. However, more attention should be paid to residual or recurrent CN during treatment, and regular long-term follow-up MRI should be mandatory to validate the procedure. Cancer 2007 © 2007 American Cancer Society.

Aims : NeuN is considered to be a marker of neuronal differentiation in brain tumours. Our aim was to perform, for the first time, a systematic and comparative analysis of NeuN expression in all major brain tumour subtypes to provide guidance for the rational use of NeuN immunohistochemistry in diagnostic histopathology. Methods and results : Anti-NeuN immunohistochemistry was performed on paraffin-embedded biopsy specimens of 106 diffuse astrocytomas, 100 pilocytic astrocytomas, 107 ependymomas, 59 1p-aberrant oligodendroglial neoplasms, 115 glioblastomas, 115 medulloblastomas, 14 gangliogliomas/gangliocytomas and 10 central neurocytomas. We found no NeuN expression in pilocytic astrocytoma, whereas all other investigated tumour subtypes showed focal or widespread expression in varying proportions of cases. Comparing NeuN expression in clear cell tumours, widespread NeuN expression had a positive predictive value of 76.9% (95% confidence interval 46.2, 95.0) for central neurocytoma. Lack of NeuN expression had a positive predictive value of 87.3% (76.5, 94.4) for oligodendroglioma. Conclusions : Immunohistochemistry can detect NeuN expression in all major brain tumour subtypes except pilocytic astrocytoma. In the individual case, assessment of NeuN expression may be helpful in the differential diagnosis of clear cell primary brain tumours but does not seem to be useful for the differential diagnosis of other brain tumour subtypes.

Extraventricular neurocytoma (EVN) is a rare brain tumor that poses diagnostic difficulty. Described herein is a case of atypical EVN arising in a 54-year-old woman. A well-circumscribed lesion (3.0 × 3.0 × 3.0 cm) in the right parietal lobe showed diffuse proliferation of monotonous tumor cells with perinuclear clearing within a delicate fibrillary matrix similar to neuropil. Tumor also showed vascular proliferation and high mitotic activity. Immunohistochemically, these tumor cells were strongly positive for synaptophysin both in the neuropil and in the perinuclear cytoplasm, and were negative for glial fibrillary acidic protein and Olig2. Ki-67 labeling index was 13.0% in the most stained areas, but accumulation of p53 was not observed. These findings were compatible with those of EVN with histological atypia. EVN should be considered as a candidate in the differential diagnosis of parenchymal brain tumor, especially oligodendroglioma. The important features are the delicate fibrillary matrix similar to neuropil, diffuse and strong immunoreactivity for synaptophysin, and negative immunoreactivity for Olig2. High proliferative activity without accumulation of p53 suggests that other factors are involved in oncogenesis of atypical EVN.

In the developing brain, neuronal differentiation is associated with permanent exit from the mitotic cycle. This raises the possibility that neuronal differentiation may suppress proliferative activity, even in neoplastic cells. As a first step towards understanding the relation between neuronal differentiation and mitotic cycling in brain tumours, we studied the expression of NeuN (a neuronal marker) and Ki-67 (a mitotic marker) by double-labelling immuno-fluorescence in 16 brain tumours with neuronal differentiation. The tumours included a series of 11 central neurocytomas, and five single cases of other tumour types. In the central neurocytomas, NeuN(+) cells had a 15-fold lower Ki-67 labelling index, on average, than did NeuN(-) cells (P < 0.01). In the other tumours (one extraventricular neurocytoma, one desmoplastic medulloblastoma, one olfactory neuroblastoma, one ganglioglioma and one anaplastic ganglioglioma), the Ki-67 labelling index was always at least fourfold lower in NeuN(+) cells than in NeuN(-) cells. These results indicate that neuronal differentiation is associated with a substantial decrease of proliferative activity in neoplastic cells of central neurocytomas, and suggest that the same may be true across diverse types of brain tumours. However, tumours with extensive neuronal differentiation may nevertheless have a high overall Ki-67 labelling index, if the mitotic activity of NeuN(-) cells is high. The correlation between NeuN expression and reduced mitotic activity in neurocytoma cells is consistent with the hypothesis that neuronal differentiation suppresses proliferation, but further studies will be necessary to determine causality and investigate underlying mechanisms.

BACKGROUND The majority of central neurocytomas are benign. Approximately 25% of these rare central nervous system tumors are more aggressive, with an MIB-1 labeling index > 2% or atypical histologic features, and are classified as atypical neurocytomas. The objective of this analysis was to define the optimal treatment for patients with these atypical tumors. METHODS The first atypical neurocytoma was described in 1989. The patients reported since then were reviewed for age, gender, extent of resection, MIB-1 index, histology, irradiation, local control, and survival. In addition to the data available in the literature, more relevant data were obtained from the authors of that literature. Treatment approaches included complete resection alone (CR), complete resection followed by radiotherapy (CR-RT), incomplete resection alone (IR), and incomplete resection followed by radiotherapy (IR-RT). These four therapies were compared for local control and survival using Kaplan–Meier analysis and the log-rank test. RESULTS Complete data were available on 85 patients (15 patients who underwent CR, 13 patients who underwent CR-RT, 17 patients who underwent IR, and 40 patients who received IR-RT). Local control rates at 3 years and 5 years were 73% and 57% after CR, 81% and 53% after CR-RT, 21% and 7% after IR, and 85% and 70% after IR-RT, respectively (P < 0.0001). Survival rates at 3 years and 5 years and were 93% and 93% after CR, 90% and 90% after CR-RT, 65% and 43% after IR, and 87% and 78% after IR-RT, respectively (P = 0.0076). CONCLUSIONS Patients who underwent CR achieved better local control and survival rates compared with patients who underwent IR. After IR, patients appeared to benefit from RT. A beneficial effect of RT after CR was not observed. Cancer 2004;100:814–7. © 2004 American Cancer Society.

BACKGROUND Central neurocytomas are composed of mature neuronal elements, frequently arranged in rosettes similar to those present in pineocytomas. This suggests the possibility of similar patterns of differentiation, including photoreceptor differentiation. The authors analyzed the immunoreactivity of central neurocytomas for retinal S-antigen, neuronal, glial, and neuroendocrine markers. METHODS Thirty-three central neurocytomas were analyzed with reference to their clinicopathologic characteristics, immunoreactivity, and the possibility that anaplastic histologic features correlated with aggressive clinical behavior. RESULTS There were 18 male and 15 female patients. The median age at diagnosis was 30 years (range, 3–69 years). All of the tumors with specified location were related to the ventricles. Thirty-two tumors were diagnosed at surgery and 1 at autopsy. Histologic features included mineralization (20 of 33), foci of necrosis (4 of 33), chronic inflammation (4 of 33), ganglion cell differentiation (1 of 33), and lipomatous differentiation (1 of 33). None of the lesions had significant nuclear pleomorphism, mitotic activity, or vascular endothelial proliferation. Immunohistochemistry included expression of synaptophysin (33 of 33), neuron specific enolase (31 of 33), S-100 protein (25 of 33), retinal S-antigen (14 of 24), somatostatin (8 of 27), glial fibrillary acidic protein (4 of 33), neurofilament protein (3 of 22), and leucine enkephalin (1 of 27). At follow-up, 15 of 23 patients were alive an average of 8.1 years (range, 0.91–35.9 years) after surgery. CONCLUSIONS Central neurocytomas behave as slowly growing neoplasms that remain confined within one or several supratentorial ventricles and are associated with long survival after surgical excision. Malignant forms with aggressive clinical behavior were not found. The neoplastic cells can express photoreceptor differentiation possibly relating central neurocytomas to pineocytomas. Adipocyte differentiation may be present, and the possibility of a relation between the central neurocytoma and cerebellar liponeurocytoma should be entertained. Cancer 2001;91:136–43. Published 2001 American Cancer Society.

BACKGROUND “Central neurocytoma” is classically considered as an intraventricular benign tumor, largely based on data from small retrospective series. The authors present prospective data on 12 patients with tumors diagnosed as central neurocytoma, to highlight the diverse nature of this tumor and challenge the classic notion. METHODS Between 1991 and 1997, 12 patients had tumors diagnosed prospectively as “central neurocytoma”. Clinical, radiologic, and histologic data were collected, and Karnofsky performance score was evaluated for each patient. Proliferation marker studies were performed using Ki-67 labeling index. RESULTS In two patients, the tumors were located in atypical locations, namely, the parietal lobe and the spine. Aggressive behavior characterized by clinical and radiologic evidence of tumor progression was noted in two additional patients. In both these cases, unusually high proliferation rates of 5.3% and 11.2% were noted. Total excision of the tumor, when possible, was the treatment of choice. Postoperative radiotherapy to the residual tumor may be of benefit in patients with clinically aggressive tumors, or those with high proliferation rates. CONCLUSIONS Given the findings of this study, it is suggested that the traditional concept of central neurocytoma as a benign intraventricular tumor warrants reconsideration. Cancer 2000;89:1111–20. © 2000 American Cancer Society.

Aims Central neurocytoma is a rare central nervous system tumour typically found in the lateral ventricles and at the septum pellucidum. Histologically, it resembles oligodendrogliomas and yet ultrastructurally, it shows neuronal differentiation. Its molecular oncogenesis is not known. The aim of this study was to examine whether major genetic events found in oligodendrogliomas and neuronal tumours, namely allelic deletions of chromosomes 1p and 19q and N-myc amplification, can be found in central neurocytomas. As there was one report describing gain of chromosome 7 in central neurocytomas, we also examined epidermal growth factor receptor (EGFR) amplification, as the EGFR gene is located at chromosome 7p. Methods and results Nine central neurocytomas and matched blood samples were examined for loss of heterozygosity (LOH) of 1p and 19q13.2–13.4 with 23 finely mapped microsatellite markers. N-myc amplification was studied by fluorescence in-situ hybridization using paraffin-embedded sections. EGFR amplification was tested for by differential PCR. Six of nine (67%) tumours showed LOH at one or more loci at 1p and 5/9 (56%) of cases showed LOH at 19q. However, common regions of deletion cannot be identified. The majority of informative markers are retained at 1p (84%) and 19q (86%). Only one tumour showed amplification of N-myc and none of the cases showed amplification of EGFR. Conclusion Central neurocytomas are genetically distinct from oligodendrogliomas, and chromosomes 1p and 19q probably do not play an important role in their pathogenesis. N-myc and EGFR amplification are rare.

BACKGROUND Recurrent central neurocytoma is very rare and to the authors' knowledge data regarding its response to chemotherapy currently are not available. METHODS Three patients with progressive neurocytoma received chemotherapy after their informed consent was obtained. Disease recurred in two patients after surgery and radiotherapy and in one patient after surgery. The treatment regimen was comprised of etoposide, 40 mg/m2/day, for 4 days; cisplatin, 25 mg/m2/day, for 4 days; and cyclophosphamide, 1000 mg/m2, on Day 4; this cycle was repeated every 4 weeks. RESULTS Stabilization of disease was observed in 2 patients and complete remission was observed in 1 patient; at last follow-up, these responses had been maintained for 15 months, 18 months, and 36 months, respectively. CONCLUSIONS In this small series, this therapeutic regimen led to long term disease reduction, and merits further study. Cancer 2000;88:169–74. © 2000 American Cancer Society.

BACKGROUND Although central neurocytomas are considered benign, recent reports suggest that some patients with histologic atypia and/or elevated proliferation potential may have a poor outcome. METHODS A retrospective review identified 15 cases of central neurocytoma. Clinical follow-up was available for 14 patients. Each tumor was evaluated for the presence of atypical histologic features, including cellular pleomorphism, endothelial proliferation, and necrosis. The proliferation potential was assessed by MIB-1 immunohistochemistry. The correlation among histology, MIB-1 labeling index (MIB-1 LI), and clinical outcome was evaluated. RESULTS Histologic atypia was identified in 3 tumors (20%). The MIB-1 LI ranged from 0.1% to 6.0%, and 5 cases (33%) had an MIB-1 LI >2%. The correlation between histologic atypia and MIB-1 LI was poor, with only 1 tumor having both atypia and MIB-1 LI >2%. Clinical follow-up ranged from 13 to 255 months postoperatively (mean, 68 months). Although most patients were alive and well at last follow-up, three developed symptomatic recurrence and one died as a result of increased tumor growth. The tumors from all 4 patients with a poor outcome had MIB-1 LI >2%, but only 1 had histologic atypia. CONCLUSIONS The proliferation potential of central neurocytoma is a useful predictor of clinical outcome, whereas histologic atypia alone is not prognostically significant. It would be appropriate to recognize a subgroup of central neurocytomas with elevated proliferation potential as WHO Grade 2 lesions. The terms "atypical" and "anaplastic" are not appropriate to describe these lesions, as they imply a certain histologic appearance. The most accurate designation would be "proliferating neurocytoma."

Human central neurocytoma cells were cultured and characterized immunophenotypically and electrophysiologically to clarify their developmental potential. We conducted systematic in vitro studies utilizing fresh tissues from three patients. Initially small homogeneous cell clusters settled down onto the bottom of the culture flasks, and, after 2 weeks from plating, mature neuron-like cells developed from these clusters and expressed neurofilament proteins (NF: specific neuronal markers). On the other hand, approximately 80% of small round cell clusters and flat glial-like cells from which these clusters developed were positively stained for glial fibrillary acidic protein (GFAP: a specific glial marker). Furthermore these neuronal and glial cells showed distinct morphology, and dual-label, indirect immunohistochemistry for GFAP and NF-200 kD disclosed that the two antigens were not found co-localized in the same cells. In single-cell clonal analysis, neuronal, glial, and mixed neuronal and glial clones were generated. Electrophysiologically, the cells of neuronal morphology possessed sodium channels, and also L-type calcium channels in whole-cell voltage clamp. The sodium channels were of a characteristic neuronal phenotype which appears in neurons. These findings suggest that small round human central neurocytoma cells exhibit both neuronal and glial differentiations and have the properties reminiscent of precursor cells derived from subventricular matrix; thus, these cultured cells may be a potential source for investigations of human CNS neuronal and glial development and differentiation.

BACKGROUND This analysis was performed to examine the outcome of patients with histologically confirmed central neurocytomas. METHODS Thirty-two patients with histologically confirmed central neurocytomas were evaluated retrospectively. Patients were treated with various combinations of surgery, chemotherapy, and radiotherapy (RT). Follow-up ranged from 2.3 to 15.3 years (median, 4.7 years). RESULTS The overall 5-year survival and local control rates were 81% and 79%, respectively. No patient developed metastases. The 5-year local control rate was 70% for patients undergoing subtotal resection (STR) and 100% for those undergoing gross total resection (GTR) (P = 0.08). The 5-year survival rate was 77% for patients undergoing STR and 90% for those undergoing GTR (P = 0.44). The effect of RT was evaluated for patients undergoing STR. The 5-year local control rate was 100% for patients who received RT after STR compared with 50% for those who did not (P = 0.02). The 5-year survival rate was 88% for patients who received RT after STR compared with 71% for those who did not (P = 0.3). Three patients received salvage RT for local progression after resection. All were alive and free of disease 1 to 6 years after RT. CONCLUSIONS GTR results in a very high likelihood of local control and survival. Postoperative RT appears to improve local control rates significantly for patients who have undergone STR. The overall prognosis of patients with central neurocytomas is quite favorable, with an actuarial 5-year survival rate of 81%. Cancer 1997; 79:790-5. © 1997 American Cancer Society.

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.

A variety of neoplasms of the human nervous system were analyzed for the presence of mutations in the p53 tumor suppressor gene. DNA was extracted from frozen or formalin-fixed, paraffin-embedded material. Single-strand conformation polymorphism (SSCP) analysis for exons 5-8 was followed by direct DNA sequencing. Mutations leading to an amino acid change were found in three of 11 (27%) low-grade (World Health Organization (WHO) Grade II) astrocytomas. They were located in codon 183 (TCA-->TGA) of exon 5, codon 237 (ATG-->ATA) of exon 7, and codon 273 (CGT-->CAT) of exon 8. In one of these cases, the sequence indicated loss of the wild-type allele. Of 12 juvenile pilocytic astrocytomas (WHO Grade I), none contained a p53 mutation, suggesting a different molecular basis for this childhood neoplasm. Except for a mutation in one of seven (14%) meningeal hemangiopericytomas (codon 238; TGT-->TTT, Cys-->Phe), no mutations were observed in exons 5-8 of the p53 gene in any of the following tumors of the nervous system and its coverings: 13 schwannomas, 12 central neurocytomas, 22 meningiomas, 10 choroid plexus papillomas and carcinomas, and 30 neuroblastomas of the sympathetic nervous system. These and published data support the view that p53 mutations are frequently involved both in low-grade and progressive (anaplastic) astrocytomas, including glioblastomas multiforme. Oligodendrogliomas, medulloblastomas, meningiomas, and hemangiopericytomas rarely (< 15%) show p53 mutations in exons 5-8, whereas none of the remaining nervous system neoplasms revealed evidence of an involvement of the p53 gene in their development.

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 “intra-ventricular” neurocytoma. Related nosologic problems of neuronal tumors of the central nervous system and their possible histogenesis are also discussed. Cancer 1992; 70:529–537.

Intraoperative cytologic evaluation of brain tumors has been used either to render a preliminary interpretation or more often as a complement to frozen section examination. Central neurocytoma is a intraventricular neoplasm, typically located in the region of the foramen of Monro, affecting mostly young to middle age adults. Histologically, central neurocytomas are characterized by monotonous cells with round nuclei and neuronal differentiation within a rich capillary network. Their distinction during intraoperative consultations from oligodendroglioma, ependymoma (mainly clear cell ependymoma), and non-Hodgkin lymphoma can be a diagnostic challenge. We report a case of a 19-year-old female with an intraventricular tumor where imprint cytology preparations were crucial for the intraoperative diagnosis of central neurocytoma. Imprint cytology preparations show a round cell neoplasm associated with neuropil clumps and short straight capillaries admixed with tumor cell clusters. To the best of our knowledge, only a few cases describing the cytologic findings of central neurocytomas have been reported in the medical literature. The differential diagnosis, tissue correlation, clinical-radiologic features, and ancillary studies are discussed. Diagn. Cytopathol. 2010. © 2009 Wiley-Liss, Inc.

SUMMARY 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.