Periventricular neurocytoma: a pathological entity

Immunohistochemical and Ultrastructural Studies of Oligodendrogliomas Revealed Features of Neuronal Differentiation

In an attempt to characterize differentiation in oligodendrogliomas, 39 cases were examined immunohistochemically with 5 neuronal markers, synaptophysin, neuron- specific enolase, neurofilament proteins, protein gene product (PGP) 9.5, and micro tubule-associated protein 2 (MAP2), in addition to glial fibrillary acidic protein (GFAP). Positive immunolabeling was obtained for neuron-specific enolose in 29 cases (74%), synaptophysin in 21 cases (54%), PGP 9.5 in 33 cases (85%), and MAP2 in 23 cases (59%). All cases were negative for neurofilament, and 90% stained for GFAP. Eight cases were further studied ultrastructurally, and in five cases features of neuronal differentiation were identified in some of the typical neoplastic oligodendro cytes—small neuritic cellular processes with microtubules and focal synapse-like junc tions, as well as sparse neurosecretory granules. It was concluded that, both immuno histochemically and ultrastructurally, oligodendrogliomas may exhibit features of neuronal differentiation. These previously unreported features of oligodendrogliomas call into question conventional immunohistochemical and electron microscopic crite ria used in distinguishing oligodendrogliomas from tumors showing similar histologic appearance, especially central neurocytomas and dysembryoplastic neuroepithelial tu mors. Int J Surg Pathol 2(1):47-56 1994

Atypical extraventricular neurocytoma

The authors report a case of atypical extraventricular neurocytoma (EVN) transformed from EVN which had been initially diagnosed as an oligodendroglioma 15 years ago. An 8-year-old boy underwent a surgical resection for a right frontal mass which was initially diagnosed as oligodendroglioma. When the tumor recurred 15 years later, a secondary operation was performed, followed by salvage gamma knife treatment. The recurrent tumor was diagnosed as an atypical EVN. The initial specimen was reviewed and immunohistochemistry revealed a strong positivity for synaptophysin. The diagnosis of the initial tumor was revised as an EVN. The patient maintained a stable disease state for 15 years after the first operation, and was followed up for one year without any complications or disease progression after the second operation. We diagnosed an atypical extraventricular neurocytoma transformed from EVN which had been initially diagnosed as an oligodendroglioma 15 years earlier. We emphasize that EVN should be included in the differential diagnosis of oligodendroglioma.

Gamma knife radiosurgery for central neurocytoma: retrospective analysis of fourteen cases with a median follow-up period of sixty-five months

OBJECT

Central neurocytoma (CN) is considered to be a benign neuronal tumor with possible atypical behavior. Microsurgery, radiation therapy (RT) and radiosurgery all have been used in treating this rare disease during the past decade. In this study, the authors present the experience with gamma knife radiosurgery (GKRS) on 14 patients with CN during a median follow-up period of 65 months and document the safety and efficacy of GKRS in the treatment of CN.

METHODS

Between November 1997 and December 2009, 14 patients pathologically diagnosed with CN were treated with GKRS. Follow-up magnetic resonance imaging (MRI) was performed at 6-month intervals. Tumor volume and adverse radiation effects (ARE) were documented to evaluate tumor response to GKRS. The Karnofsky Performance Scale (KPS) and neurological status were used to assess clinical outcome. The mean radiation dose prescribed to the tumor margin was 12.1 Gy (ranging from 11 to 13 Gy). The mean tumor volume was 19.6 ml (ranging from 3.5 to 48.9 ml). The mean follow-up period was 70 months (ranging from 30 to 140 months), and the median follow-up period was 65 months.

RESULTS

Tumor shrinkage was found in all patients at the final MRI follow-up. The mean volume reduction was 69% (ranging from 47 to 87%). No tumor progression, ARE or radiation-related toxicity developed in any of the cases. The KPS scores of all patients were the same or had increased, and the neurological functions were all stable without deterioration at the final follow-up.

CONCLUSION

In our observations, GKRS was found to be an effective and safe alternative as adjuvant therapy for pathology-confirmed CN. The tumor volume and functional outcome can be controlled with a favorable result in long-term observation. Compared with RT and microsurgery, GKRS plays an important role in the treatment of CN as a minimally invasive technique with low morbidity. Regular long-term MRI follow-up should be mandatory to document the tumor response and possible recurrence. Multicenter consortia should be considered for further investigation and evaluation of GKRS for such a rare tumor.

Central neurocytoma: Management recommendations based on a 35-year experience

PURPOSE

To examine the outcomes of patients with histologically confirmed central neurocytomas.

METHODS AND MATERIALS

The data from 45 patients with central neurocytomas diagnosed between 1971 and 2003 were retrospectively evaluated. Various combinations of surgery, radiotherapy (RT), and chemotherapy had been used for treatment.

RESULTS

The median follow-up was 10.0 years. The 10-year overall survival and local control rate was 83% and 60%, respectively. Patients whose tumor had a mitotic index of <3 (per 10 high-power fields) experienced a 10-year survival and local control rate of 89% and 74%, respectively, compared with 57% (p = 0.040) and 46% (p = 0.14) for patients with a tumor mitotic index of > or =3. The 10-year survival and local control rate was 90% and 74% for patients with typical tumors compared with 63% (p = 0.055) and 46% (p = 0.41) for those with atypical tumors. A comparison of gross total resection with subtotal resection showed no significant difference in survival or local control. Postoperative RT improved local control at 10 years (75% with RT vs. 51% without RT, p = 0.045); however, this did not translate into a survival benefit. No 1p19q deletions were found in the 19 tumors tested.

CONCLUSION

Although the overall prognosis is quite favorable, one-third of patients experienced tumor recurrence or progression at 10 years, regardless of the extent of the initial resection. Postoperative RT significantly improved local control but not survival, most likely because of the effectiveness of salvage RT. For incompletely resected atypical tumors and/or those with a high mitotic index, consideration should be given to adjuvant RT because of the more aggressive nature.

Central neurocytoma: a novel appraisal of a polymorphic pathology. Our experience and a review of the literature

Central neurocytoma should be considered in the differential diagnosis of intraventricular tumours. The records of 20 patients operated on between 1975 and 2000 for central neurocytoma were retrospectively reviewed, and the histological gradings and clinical outcomes were compared. On the basis of our previous cases, in the latter five of this series, the following therapeutic protocol was adopted. In those cases in which total removal was achieved, no further treatment was given if the MIB-1 index was <4%; vice versa, if it was >4%, a course of conformational radiotherapy was delivered. In subtotally removed cases, radiosurgery with linac was also performed (median dose 20 Gy) as well as conformational radiotherapy whenever there was a recurrence of the lesion (median dose 45 Gy). In cases in which there was only partial cytoreduction, conformational radiotherapy was administered with the adjunct of polychemotherapy if the MIB-1 was >4%. Twenty patients were surgically treated: 11 men and nine women, with an average age of 26 years (range 17 years to 42 years).Total, subtotal and partial removals were achieved in, respectively, ten, three and seven cases. At average follow-up of 7 years, 16 patients had been cured, had significantly improved or were at least stable [Karnofsky performance status score (KPS)] >70 or more)]. On the other hand, four patients had worsened; of these, two had died and two had a KPS=50 and an unfavourable prognosis. The presence of histological atypia has proved to be a significantly negative risk factor for survival (P=0.02) while an MIB score >4% was significantly correlated with an unfavourable outcome (death or worsening of neurological status). The "atypical" neurocytoma seems to be a distinct entity, with a less favourable prognosis and a higher tendency to recur.

Intraventricular neurocytoma with massive brain stem involvement in a 5-year-old child

INTRODUCTION

Central neurocytoma is a tumor of neuronal origin that should be taken into consideration in the differential diagnosis of intraventricular neoplasms. Reports of neurocytomas with an extraventricular localization are rare: to our knowledge, the case described here is the first in which a neurocytoma developed within the ventricles but also invaded the brain stem.

CASE REPORT

The authors describe the unusual case of a 5-year-old boy with an intraventricular neurocytoma presenting with massive involvement of the basal nuclei and the brain stem. The patient underwent first biopsy and then surgery for ventricular-peritoneal shunting and partial removal of the tumor. Histology showed the tumor to be a typical neurocytoma with Mib-1 <2%. The postoperative course was uneventful. At 3 years' follow-up, the patient's clinical condition is stable and there are no signs of disease progression.

DISCUSSION

The literature is reviewed and the characteristics of this unusual tumor are discussed.

Atypical extraventricular neurocytoma with oligodendroglioma-like spread and an unusual pattern of chromosome 1p and 19q loss

An insular cortex tumor in a 54-year-old woman showed unequivocal neurocytic features, including open nuclei, distinct nucleoli, and strong synaptophysin immunoreactivity. Ultrastructurally, there were neuritic-type processes with microtubules and hillock-like attachments, and there were dense-core granules. Atypical features were mitotic activity, prominent vasculature, and small foci of necrosis. Peripherally, there was oligodendroglia-like histology with single-cell infiltration of white matter and perineuronal spread in cortex. Fluorescence in situ hybridization analysis with chromosome 1 and 19 probes showed 3 copies of 1q and 2 copies of 1p and showed 2 copies of 19q and 4 copies of 19p. This yielded a 1p-19q loss of heterozygosity pattern similar to that seen in oligodendrogliomas, although the actual chromosomal abnormality is distinct. This tumor, best classified as an atypical neurocytoma with oligodendroglia-like spread, supports suggestions of a close histogenic relationship between oligodendroglial and neurocytic tumors. This case also illustrates the limitations of relying exclusively on loss of heterozygosity analysis for tumor classification.

Gamma knife surgery for treatment of central neurocytomas. Report of four cases

The authors investigated the use of gamma knife surgery (GKS) in the treatment of central neurocytoma, a usually benign primary brain tumor of the lateral and third ventricles. Four patients with subtotally resected or recurrent central neurocytomas were retrospectively studied. The prescription isodose was 9 to 13 Gy to the 30 to 50% peripheral isodose line. Pre- and postoperative magnetic resonance (MR) images were compared to determine the volume reduction following GKS. Follow-up review included annual MR imaging and clinical evaluation by a neurosurgeon. Follow-up periods ranged from 12 to 99 months. Marked reduction in tumor size was seen in all four patients; the decrease in tumor volume for each was 48%, 72%, 81%, and 77%, respectively, at the last follow-up review. None of the four patients required additional treatment and none experienced a decline in neurological function during the follow-up period. No complications have been noted in any of these patients to date. Even though there have been few observations and follow-up time has been limited, because of the consistency of the response and the lack of observed side effects, GKS may be the treatment of choice for subtotally resected and recurrent central neurocytomas.

Central neurocytoma with malignant course. Neuronal and glial differentiation and craniospinal dissemination

Central neurocytoma is a benign neuronal tumor of young adults in the lateral cerebral ventricles with characteristic X ray and light microscopic findings. In many respects typical central neurocytoma is reported below, with recurrence in the third month requiring reoperation. Death ensued in the fifth postoperative month. Subsequent histology proved progressive vascular proliferation and increasing, unusual glial differentiation of the neuronal tumor. At autopsy tumorous seeding blocked the liquor circulation. A thin tumorous layer covered the surface of all ventricles, the cerebellum and medulla oblongata. The GFAP positive cells out-numbered the synaptophysin positive ones. Increase of GFAP positivity and vascular proliferation of the central neurocytoma may be alarming signs suggesting a malignant course in addition to the other atypical features.

A study of proliferative markers in central neurocytoma

To gain a better insight into the biological behavior of central neurocytomas, various proliferative indices were studied in these tumors and correlated with the histological features as well as the clinical outcome. Twenty cases of neurocytoma were selected over a 16 year period (1980-1995), which accounted for 0.28% of all intracranial tumors reported at this centre. Treatment consisted of surgical resection (total 14, subtotal six) followed by radiotherapy. Except for five patients who died of surgical complications, the remaining 15 were all alive and well during the follow-up period, varying from six months to 72 months (average 32 months). Thirteen tumors showed benign histological characteristics (Group I) while seven showed mitoses + necrosis (Group II). The proliferative index was assessed in formalin-fixed paraffin-embedded tissue of 17 cases using the silver nucleolar organiser region (AgNOR) technique and immunohistochemical staining for proliferating cell nuclear antigen (PCNA-PC10 antibody) and Ki-67 antigen (MIB-1 monoclonal antibody). The AgNOR counts ranged from 1.2 to 2.6 (mean 1.9 +/- 0.4), PCNA labeling index (LI) from 0.1 to 5.5 (mean 2.5 +/- 1.8) and MIB-1 LI from 0.1 to 3 (mean 0.8 +/- 0.02). There was no significant difference in any of these parameter values between histological Groups I and II, except that MIB-1 LI tended to be higher in Group II tumors. Further, there was no significant correlation between these proliferative indices and the mitotic rate of the tumors as well as the survival of the patients. A longer follow-up will be required to determine the relationship between proliferative markers and outcome as well as to bring out any heterogeneity in their biological behavior. Since these are relatively rare tumors, multicentric pooling of data will be required to reach a definitive consensus regarding their biological aggressiveness and consequentially, the use of radiotherapy in their treatment. The present report is a contribution in this direction.

Central neurocytoma: a clinical study of response to chemotherapy

We report a case of central neurocytoma treated, after an initial partial resection, by chemotherapy, comprising etoposide, ifosfamide and carboplatin. A response was obtained and further treatment was given with surgery and radiotherapy. There have been no previous reports of response to chemotherapy in this relatively rare tumour.

Ultrastructural characteristics of central neurocytoma in cell culture

The study was performed to determine the ultrastructural characteristics of central neurocytoma and its features in primary cell culture. Fresh tissue from three tumors was mechanically and enzymatically dissociated into individual cells, which were cultured onto poly-L-lysine precoated Aclar coverslips in the media. The tumor cells attached to the surface of the coverslips within 12 to 24 h and delicate cytoplasmic processes developed within 2 to 3 days. Electron microscopic examination of the cultured tumor cells and the tumor tissue supported neuronal origin. Combined tissue culture and electron microscopic study provides a rapid, reliable, and reproducible means for the diagnosis of central neurocytoma.

Central neurocytoma: the role of radiation therapy and long term outcome

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.

Proliferative activity of central neurocytoma: measurement of tumor volume doubling time, MIB-1 staining index and bromodeoxyuridine labeling index

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.

Craniospinal dissemination of central neurocytoma. Report of two cases

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.

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.

Cerebral neurocytoma: an unusual cause of refractory epilepsy. Case report and review of the literature

We report a patient with medically refractory complex partial seizures (CPS) caused by a cerebral neurocytoma located near the amygdala. Neurocytoma represents an important addition to the differential diagnosis and, in particular, must be differentiated from oligodendroglioma and dysembryoplastic neuroepithelial tumor. Accurate pathological differential has therapeutic and prognostic implications.

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.

Giant central neurocytoma with tetraventricular and extra-axial extension. Case report

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.

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.

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.

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.