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Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle: Case report and review of literature
Clinical Neurology and Neurosurgery 112 (2010) 362–364
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Case report
Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle: Case report and review of literature夽 ShiHai Luan, DongXiao Zhuang, LinLin Sun, Feng-Ping Huang ∗ Department of Neurosurgery, Huashan Hospital affiliated to Fudan University, Shanghai Neurosurgical Center, The 3rd ward, 12 Middle Wulumuqi Road, Shanghai 200040, PR China
a r t i c l e
i n f o
Article history: Received 7 August 2009 Received in revised form 9 January 2010 Accepted 11 January 2010 Available online 4 February 2010 Keywords: Rosette-forming Glioneuronal tumor Cerebellum
a b s t r a c t Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle has been identified as a novel and distinctive type of primary central nervous system neoplasm. In this report, we present a case with RGNT arising from the right cerebellar hemisphere. A 30-year-old female patient complained of headache for a five-year duration. Preoperative MRI revealed a well-circumscribed, cystic-solid lesion with hypo-intensity on T1-weighted image, hyper-intensity on T2-weighted image, and significant dotlike enhancement after IV contrast. Gross total resection was achieved in this case via suboccipital retro-sigmoidal approach, and RGNT was confirmed in the final histopathological diagnosis. RGNT of the fourth ventricle is a rare, benign tumor with an excellent prognosis. Operation is recommended as the prior protocol of treatment, and the follow-up MRI is necessary to evaluate the long-term prognostic effects. Currently, only one case of progression or recurrence has been reported in the postoperative course. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved.
1. Introduction Due to its distinct clinicopathological features, the Rosetteforming glioneuronal tumor (RGNT) of the fourth ventricle is now recognized as a novel entity in the newly updated WHO classification of tumors in the central nervous system [1]. Typically, RGNTs are midline lesions centered in the fourth ventricle and mainly observed in cerebellar localization [2]. Based on the English literature, more than 30 cases of RGNT have been reported previously. In this report, we present a case of RGNT deriving from the right cerebellum and review the literature. 2. Case report 2.1. Clinical history This 30-year-old female presented with headache for 5 years, and neurological examination disclosed no abnormalities. Magnetic Resonance Imaging (MRI) demonstrated that a 2.5 cm × 1.5 cm solitary cystic-solid lesion was situated in the right
夽 Disclaimer: This paper has not been published elsewhere in whole or in part. All authors have read and approved the content, and agreed to submit for consideration for publication in the journal. There are no ethical/legal conflicts involved in the article. ∗ Corresponding author. Tel.: +86 21 62489999; fax: +86 21 50301919. E-mail address: [email protected] (F.-P. Huang).
cerebellar hemisphere. Its location was away from the fourth ventricle and close to the right cerebellar pontine angle, which was not characteristically in midline parts centered in the fourth ventricle as reported. The solid component of the tumor appeared hypo-intense in T1-weighted imaging (Fig. 1A), and hyper-intense in T2-weighted imaging (Fig. 1B), with significant dotted enhancement (Fig. 1C and D). 2.2. Pathological findings Microscopically, the tumor exhibited both a neurocytic and an astrocytic component. In the neurocytic components, neurocytes formed neurocytic rosettes (Fig. 2A). At the center of the neurocytic rosettes was an eosinophilic core, displaying strong positive staining with synaptophysin (Fig. 2B) and Olig2 (Fig. 2C), while the astrocytic components of the tumor showed that the tumor cells had bipolar and spindle processes with positive immunostaining of GFAP(Fig. 2D), and the nuclei of the tumor cells were round and oval. The MIB-1 labeling index was about 1%. Reticular tumor cells were locally scattered, and occasionally Rosenthal fibers were observed. The final pathological diagnosis was a typical rosette-forming glioneuronal tumor (WHO Grade I). 2.3. Treatment and follow-up Total resection was performed by right suboccipital retrosigmoidal approach. At surgery, it was observed that the solitary
0303-8467/$ – see front matter. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.clineuro.2010.01.006
S. Luan et al. / Clinical Neurology and Neurosurgery 112 (2010) 362–364
363
Fig. 1. Coronal MRI disclosed a cystic-solid lesion located in right cerebellar hemisphere, the tumor appeared hypo-intense in T1-weighted imaging (A), and hyper-intense in T2-weighted imaging (B). The solid component of the tumor appeared dotted enhancement (C, D).
tumor arised from the right cerebellum and appeared relatively soft, gray, fresh, and well demarcated. Postoperatively, the patient’s headache was totally relieved, without postoperative cranial nerve deficits .The patient was discharged from the hospital 10 days later, and no recurrence and postoperative neurological complications have been observed during 9 months’ follow-up.
3. Discussion The RGNT of the fourth ventricle was initially described in 1995 as a cerebellar form of dysembryoplastic neuroepithelial tumor [3], and Komori et al. introduced the term RGNT of the fourth ventricle in their original description of 11 patients in 2002 [4]. In the newly updated WHO classification of tumors
Fig. 2. (A) A typical component of neurocytic rosette, nuclei are arranged in ring-like arrays around eosinophilic neuropil cores (hematoxylin and eosin staining ×400). (B) The neuropil cores of neurocytic rosettes displays strong immunoreactivity for synaptophysin (immuno-peroxidase ×400). (C) Immunochemistry shows Olig2 is strongly positive (immuno-peroxidase ×400). (D) Immunohistochemistry for GFAP exhibits strong reactivity of the astrocytic tumor component (immuno-peroxidase ×400).
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S. Luan et al. / Clinical Neurology and Neurosurgery 112 (2010) 362–364
of the central nervous system, it is confirmed as a new type [2]. As uncommon lesions, the population-based incidence of RGNTs is unknown [2]. According to Komori et al. [4], RGNTs of the fourth ventricle preferentially affected young adults, and the average age of the patients at diagnosis was 31.5 years (range 12–59). Older patients may also be affected; two cases of patients with age over 65 years have been represented by Rosenblum [2]. The male/female ratio was 1:1.75. Clinical symptoms and signs lack specificity, including headache with high intracranial pressure due to an increase of volume, cerebellar ataxia, dysarthria, and vertigo. Headache was the most common presenting symptom in the series of Komori et al. [4], and was confirmed by other reports [5]. Also, rare manifestations, such as brainstem dysfunction, neck pain and rigidity, have been noted. Asymptomatic patients were found, and no sudden onset of symptoms with acute clinical course has been described in RGNT so far [6]. Radiologically, it is typically shown that most RGNTs are midline lesions, centered in the fourth ventricle, and limited extension into the cerebellar vermis, brainstem and cerebral aqueduct may be noted [2]. Tumors primarily situated in the tectal/pineal and acqueductal regions are documented [4,7], as are multifocal lesions with fourth ventricular, vermian, dorsal pontine and, in one case, mesencephalic and thalamic components [2,4]. Recently, rare locations of RGNTs, including spinal cord and optic chiasm, have been reported [8,9]. Occurrence of RGNTs in the posterior fossa and association with the fourth ventricle is a typical feature of most reported cases, and it could be unifocal, occasionally multifocal. On CT scan, the solid parts of the tumor are usually hypo-intense, and the cystic parts with lower intensity. Dense calcification could be seen occasionally and may be extensive. On MR evaluation, T1iso/hypo-intensity and T2-hyper-intensity are the rule. RGNTs are relatively circumscribed, may be solid, cystic-solid, or multi-cystic, and usually display at least focal contrast-enhancement that may be nodular, linear, ring or spot-like, which is relatively specific [2]. Satellite lesions could be detected. There may be related edema or hydrocephalus, which is generally minimal. Tumor dimensions range in size from 1 to 5 cm (mean, 3.3 cm) [2]. In our view, other lesions in the similar positions should be included in the radiological differential diagnosis, such as cystic hemangioblastoma, pilocytic astrocytoma, medulloblastoma, ependymoma, choroidal papilloma as well. Histologically, the striking feature is that the tumors exhibit two major components. The first consists of uniform neurocytes engaged in the formation of neurocytic rosettes as well as perivascular pseudorosettes, while the second component consists of spindle to stellate astrocytes with elongation to oval nuclei and moderately dense chromatin in a dense background of fibrillary processes. Occasional Rosenthal fibers and eosinophilic granular bodies were identified [4]. Immunohistochemistry studies show positive reactivity of GFAP for the oligodendroglioma tumor
component. The neuropil cores of neurocytic rosettes show no immunoreactivity for any of the glial markers, but display strong immunoreactivity for synaptophysin. RGNT lacks histopathological signs of malignancy. Tumor cell proliferation indices as assessed by MIB-1 labeling of Ki-67 antigen are low, and there is no or only little increase of tumor mass over time. The MIB-1 staining of the Ki67 antigen is 0.35–3.07, and the mean value is 1.58% [4,10]. It should be pointed out that dysembryoplastic neuroepithelial tumor (DNET) of the cerebellum and papillary glioneuronal tumor (PGNT) are important differential diagnosis for RGNT, which display histopathological features similar to RGNT [3,11]. In our opinion, the prior protocol of treatment is operation, and radiotherapy or chemotherapy is not recommended. According to previous documentation, most of the patients with RGNTs experienced no recurrence, regardless of extent of resection; while only one case was reported to suffer from a recurrence at 120 months although the details of the first surgery were unavailable [7]. Thus, its biologic behavior is clearly inactive, corresponding to WHO Grade I. Nevertheless, due to sites of RGNTs, some patients have complicated postoperative courses and experience neurological deficits [4]. Routine follow-up examination of skull MRI will be recommended in order to estimate the long-term prognosis. References [1] Louis DN, Ohgaki H, Wiestler OD. WHO Classification of Tumours of the Central Nervous System. Lyon, France: IARC Press; 2007. pp. 115–116. [2] Rosenblum MK. The 2007 WHO classification of nervous system tumors: newly recognized members of the mixed glioneuronal group. Brain Pathol 2007;17:308–13. [3] Kuchelmeister K, Demirel T, Schlörer E, Bergmann M, Gullotta F. Dysembryoplastic neuroepithelial tumour of the cerebellum. Acta Neuropathol 1995;89:385–90. [4] Komori T, Scheithauer BW, Hirose T. A rosette-forming glioneuronal tumor of the fourth ventricle: infratentorial form of dysembryoplastic neuroepithelial tumor? Am J Surg Pathol 2002;26:582–91. [5] Surawicz TS, McCarthy BJ, Kupelian V, Jukich PJ, Bruner JM, Davis FG. Descriptive epidemiology of primary brain and CNS tumors: results from the Central Brain Tumor Registry of the United States, 1990–1994. Neuro-oncol 1999;1:14–25. [6] Franz Marhold, Matthias Preusser, Wolfgang Dietrich, Daniela Prayer, Thomas Czech. Clinicoradiological features of rosette-forming glioneuronaltumor (RGNT) of the fourth ventricle: report of four cases and literature review. J Neurooncol 2008;90:301–8. [7] Jacques TS, Eldridge C, Patel A, Saleem NM, Powell M, Kitchen ND, Thom M, Revesz T. Mixed glioneuronal tumor of the fourth ventricle with prominent rosette formation. Neuropathol Appl Neurobiol 2006;32:217–20. [8] Anan M, Inoue R, Ishii K, Abe T, Fujiki M, Kobayashi H, Goya T, Nakazato Y. A rosette-forming glioneuronal tumor of the spinal cord: the first case of a rosette-forming glioneuronal tumor originating from the spinal cord. Hum Pathol 2009;40:898–901. [9] Scheithauer BW, Silva AI, Ketterling RP, Pula JH, Lininger JF, Krinock MJ. Rosette-forming glioneuronal tumor: report of a chiasmal-optic nerve example in neurofibromatosis type 1: special pathology report. Neurosurgery 2009;64:771–2. [10] Vajtai I, Arnold M, Kappeler A, Jeless O, Lukes A, Mariani L, Paulus Werner. Rosette-forming glioneuronal tumor of the fourth ventricle: Report of two cases with a differential diagnostic overview. Pathol Res Pract 2007;203:613–9. [11] Komori T, Scheithauer BW, Anthony DC, et al. Papillary glioneuronal tumor: a new variant of mixed neuronal-glial neoplasm. Am J Surg Pathol 1998;22:1171–83.
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Case report
Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle: Case report and review of literature夽 ShiHai Luan, DongXiao Zhuang, LinLin Sun, Feng-Ping Huang ∗ Department of Neurosurgery, Huashan Hospital affiliated to Fudan University, Shanghai Neurosurgical Center, The 3rd ward, 12 Middle Wulumuqi Road, Shanghai 200040, PR China
a r t i c l e
i n f o
Article history: Received 7 August 2009 Received in revised form 9 January 2010 Accepted 11 January 2010 Available online 4 February 2010 Keywords: Rosette-forming Glioneuronal tumor Cerebellum
a b s t r a c t Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle has been identified as a novel and distinctive type of primary central nervous system neoplasm. In this report, we present a case with RGNT arising from the right cerebellar hemisphere. A 30-year-old female patient complained of headache for a five-year duration. Preoperative MRI revealed a well-circumscribed, cystic-solid lesion with hypo-intensity on T1-weighted image, hyper-intensity on T2-weighted image, and significant dotlike enhancement after IV contrast. Gross total resection was achieved in this case via suboccipital retro-sigmoidal approach, and RGNT was confirmed in the final histopathological diagnosis. RGNT of the fourth ventricle is a rare, benign tumor with an excellent prognosis. Operation is recommended as the prior protocol of treatment, and the follow-up MRI is necessary to evaluate the long-term prognostic effects. Currently, only one case of progression or recurrence has been reported in the postoperative course. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved.
1. Introduction Due to its distinct clinicopathological features, the Rosetteforming glioneuronal tumor (RGNT) of the fourth ventricle is now recognized as a novel entity in the newly updated WHO classification of tumors in the central nervous system [1]. Typically, RGNTs are midline lesions centered in the fourth ventricle and mainly observed in cerebellar localization [2]. Based on the English literature, more than 30 cases of RGNT have been reported previously. In this report, we present a case of RGNT deriving from the right cerebellum and review the literature. 2. Case report 2.1. Clinical history This 30-year-old female presented with headache for 5 years, and neurological examination disclosed no abnormalities. Magnetic Resonance Imaging (MRI) demonstrated that a 2.5 cm × 1.5 cm solitary cystic-solid lesion was situated in the right
夽 Disclaimer: This paper has not been published elsewhere in whole or in part. All authors have read and approved the content, and agreed to submit for consideration for publication in the journal. There are no ethical/legal conflicts involved in the article. ∗ Corresponding author. Tel.: +86 21 62489999; fax: +86 21 50301919. E-mail address: [email protected] (F.-P. Huang).
cerebellar hemisphere. Its location was away from the fourth ventricle and close to the right cerebellar pontine angle, which was not characteristically in midline parts centered in the fourth ventricle as reported. The solid component of the tumor appeared hypo-intense in T1-weighted imaging (Fig. 1A), and hyper-intense in T2-weighted imaging (Fig. 1B), with significant dotted enhancement (Fig. 1C and D). 2.2. Pathological findings Microscopically, the tumor exhibited both a neurocytic and an astrocytic component. In the neurocytic components, neurocytes formed neurocytic rosettes (Fig. 2A). At the center of the neurocytic rosettes was an eosinophilic core, displaying strong positive staining with synaptophysin (Fig. 2B) and Olig2 (Fig. 2C), while the astrocytic components of the tumor showed that the tumor cells had bipolar and spindle processes with positive immunostaining of GFAP(Fig. 2D), and the nuclei of the tumor cells were round and oval. The MIB-1 labeling index was about 1%. Reticular tumor cells were locally scattered, and occasionally Rosenthal fibers were observed. The final pathological diagnosis was a typical rosette-forming glioneuronal tumor (WHO Grade I). 2.3. Treatment and follow-up Total resection was performed by right suboccipital retrosigmoidal approach. At surgery, it was observed that the solitary
0303-8467/$ – see front matter. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.clineuro.2010.01.006
S. Luan et al. / Clinical Neurology and Neurosurgery 112 (2010) 362–364
363
Fig. 1. Coronal MRI disclosed a cystic-solid lesion located in right cerebellar hemisphere, the tumor appeared hypo-intense in T1-weighted imaging (A), and hyper-intense in T2-weighted imaging (B). The solid component of the tumor appeared dotted enhancement (C, D).
tumor arised from the right cerebellum and appeared relatively soft, gray, fresh, and well demarcated. Postoperatively, the patient’s headache was totally relieved, without postoperative cranial nerve deficits .The patient was discharged from the hospital 10 days later, and no recurrence and postoperative neurological complications have been observed during 9 months’ follow-up.
3. Discussion The RGNT of the fourth ventricle was initially described in 1995 as a cerebellar form of dysembryoplastic neuroepithelial tumor [3], and Komori et al. introduced the term RGNT of the fourth ventricle in their original description of 11 patients in 2002 [4]. In the newly updated WHO classification of tumors
Fig. 2. (A) A typical component of neurocytic rosette, nuclei are arranged in ring-like arrays around eosinophilic neuropil cores (hematoxylin and eosin staining ×400). (B) The neuropil cores of neurocytic rosettes displays strong immunoreactivity for synaptophysin (immuno-peroxidase ×400). (C) Immunochemistry shows Olig2 is strongly positive (immuno-peroxidase ×400). (D) Immunohistochemistry for GFAP exhibits strong reactivity of the astrocytic tumor component (immuno-peroxidase ×400).
364
S. Luan et al. / Clinical Neurology and Neurosurgery 112 (2010) 362–364
of the central nervous system, it is confirmed as a new type [2]. As uncommon lesions, the population-based incidence of RGNTs is unknown [2]. According to Komori et al. [4], RGNTs of the fourth ventricle preferentially affected young adults, and the average age of the patients at diagnosis was 31.5 years (range 12–59). Older patients may also be affected; two cases of patients with age over 65 years have been represented by Rosenblum [2]. The male/female ratio was 1:1.75. Clinical symptoms and signs lack specificity, including headache with high intracranial pressure due to an increase of volume, cerebellar ataxia, dysarthria, and vertigo. Headache was the most common presenting symptom in the series of Komori et al. [4], and was confirmed by other reports [5]. Also, rare manifestations, such as brainstem dysfunction, neck pain and rigidity, have been noted. Asymptomatic patients were found, and no sudden onset of symptoms with acute clinical course has been described in RGNT so far [6]. Radiologically, it is typically shown that most RGNTs are midline lesions, centered in the fourth ventricle, and limited extension into the cerebellar vermis, brainstem and cerebral aqueduct may be noted [2]. Tumors primarily situated in the tectal/pineal and acqueductal regions are documented [4,7], as are multifocal lesions with fourth ventricular, vermian, dorsal pontine and, in one case, mesencephalic and thalamic components [2,4]. Recently, rare locations of RGNTs, including spinal cord and optic chiasm, have been reported [8,9]. Occurrence of RGNTs in the posterior fossa and association with the fourth ventricle is a typical feature of most reported cases, and it could be unifocal, occasionally multifocal. On CT scan, the solid parts of the tumor are usually hypo-intense, and the cystic parts with lower intensity. Dense calcification could be seen occasionally and may be extensive. On MR evaluation, T1iso/hypo-intensity and T2-hyper-intensity are the rule. RGNTs are relatively circumscribed, may be solid, cystic-solid, or multi-cystic, and usually display at least focal contrast-enhancement that may be nodular, linear, ring or spot-like, which is relatively specific [2]. Satellite lesions could be detected. There may be related edema or hydrocephalus, which is generally minimal. Tumor dimensions range in size from 1 to 5 cm (mean, 3.3 cm) [2]. In our view, other lesions in the similar positions should be included in the radiological differential diagnosis, such as cystic hemangioblastoma, pilocytic astrocytoma, medulloblastoma, ependymoma, choroidal papilloma as well. Histologically, the striking feature is that the tumors exhibit two major components. The first consists of uniform neurocytes engaged in the formation of neurocytic rosettes as well as perivascular pseudorosettes, while the second component consists of spindle to stellate astrocytes with elongation to oval nuclei and moderately dense chromatin in a dense background of fibrillary processes. Occasional Rosenthal fibers and eosinophilic granular bodies were identified [4]. Immunohistochemistry studies show positive reactivity of GFAP for the oligodendroglioma tumor
component. The neuropil cores of neurocytic rosettes show no immunoreactivity for any of the glial markers, but display strong immunoreactivity for synaptophysin. RGNT lacks histopathological signs of malignancy. Tumor cell proliferation indices as assessed by MIB-1 labeling of Ki-67 antigen are low, and there is no or only little increase of tumor mass over time. The MIB-1 staining of the Ki67 antigen is 0.35–3.07, and the mean value is 1.58% [4,10]. It should be pointed out that dysembryoplastic neuroepithelial tumor (DNET) of the cerebellum and papillary glioneuronal tumor (PGNT) are important differential diagnosis for RGNT, which display histopathological features similar to RGNT [3,11]. In our opinion, the prior protocol of treatment is operation, and radiotherapy or chemotherapy is not recommended. According to previous documentation, most of the patients with RGNTs experienced no recurrence, regardless of extent of resection; while only one case was reported to suffer from a recurrence at 120 months although the details of the first surgery were unavailable [7]. Thus, its biologic behavior is clearly inactive, corresponding to WHO Grade I. Nevertheless, due to sites of RGNTs, some patients have complicated postoperative courses and experience neurological deficits [4]. Routine follow-up examination of skull MRI will be recommended in order to estimate the long-term prognosis. References [1] Louis DN, Ohgaki H, Wiestler OD. WHO Classification of Tumours of the Central Nervous System. Lyon, France: IARC Press; 2007. pp. 115–116. [2] Rosenblum MK. The 2007 WHO classification of nervous system tumors: newly recognized members of the mixed glioneuronal group. Brain Pathol 2007;17:308–13. [3] Kuchelmeister K, Demirel T, Schlörer E, Bergmann M, Gullotta F. Dysembryoplastic neuroepithelial tumour of the cerebellum. Acta Neuropathol 1995;89:385–90. [4] Komori T, Scheithauer BW, Hirose T. A rosette-forming glioneuronal tumor of the fourth ventricle: infratentorial form of dysembryoplastic neuroepithelial tumor? Am J Surg Pathol 2002;26:582–91. [5] Surawicz TS, McCarthy BJ, Kupelian V, Jukich PJ, Bruner JM, Davis FG. Descriptive epidemiology of primary brain and CNS tumors: results from the Central Brain Tumor Registry of the United States, 1990–1994. Neuro-oncol 1999;1:14–25. [6] Franz Marhold, Matthias Preusser, Wolfgang Dietrich, Daniela Prayer, Thomas Czech. Clinicoradiological features of rosette-forming glioneuronaltumor (RGNT) of the fourth ventricle: report of four cases and literature review. J Neurooncol 2008;90:301–8. [7] Jacques TS, Eldridge C, Patel A, Saleem NM, Powell M, Kitchen ND, Thom M, Revesz T. Mixed glioneuronal tumor of the fourth ventricle with prominent rosette formation. Neuropathol Appl Neurobiol 2006;32:217–20. [8] Anan M, Inoue R, Ishii K, Abe T, Fujiki M, Kobayashi H, Goya T, Nakazato Y. A rosette-forming glioneuronal tumor of the spinal cord: the first case of a rosette-forming glioneuronal tumor originating from the spinal cord. Hum Pathol 2009;40:898–901. [9] Scheithauer BW, Silva AI, Ketterling RP, Pula JH, Lininger JF, Krinock MJ. Rosette-forming glioneuronal tumor: report of a chiasmal-optic nerve example in neurofibromatosis type 1: special pathology report. Neurosurgery 2009;64:771–2. [10] Vajtai I, Arnold M, Kappeler A, Jeless O, Lukes A, Mariani L, Paulus Werner. Rosette-forming glioneuronal tumor of the fourth ventricle: Report of two cases with a differential diagnostic overview. Pathol Res Pract 2007;203:613–9. [11] Komori T, Scheithauer BW, Anthony DC, et al. Papillary glioneuronal tumor: a new variant of mixed neuronal-glial neoplasm. Am J Surg Pathol 1998;22:1171–83.