Romanian Neurosurgery (2019) XXXIII (3): pp. 232-238 DOI: 10.33962/roneuro-2019-039 www.journals.lapub.co.uk/index.php/roneurosurgery Anatomical localization of intracranial grade II meningiomas in North-Eastern Romania. Our 25-years experience A.I. Cucu1, Claudia Florida Costea1,2, Mihaela Dana Turliuc1,2, Cristina Mihaela Ghiciuc2, B.Costachescu1,2, Roxana Popescu1,2, Gabriela Florenta Dumitrescu1, Anca Sava1,2, Daniela Maria Tanase2, R. Arbore-Sorete1, I. Poeata1,2 1 "Prof. Dr. N. Oblu" Emergency Clinical Hospital Iași, ROMANIA 2 "Grigore T. Popa" University of Medicine and Pharmacy Iași, ROMANIA ABSTRACT Objective. Our research aims to assess a possible connection between tumour localization and histological subtypes of grade II meningiomas. Material and methods. 143 patients with grade II WHO meningiomas underwent surgical resection in "Prof. Dr. N. Oblu" Emergency Clinical Hospital Iași between 1990 and 2015. The collected data included: patient age, gender, tumour localization and histopathological diagnosis (atypical, clear cells and chordoid meningioma). Results. 135 (94.4%) of all 143 patients with grade II meningiomas were atypical meningiomas, 6 (4.2%) were cell clear meningiomas and only 2 (1.4%) were chordoid meningiomas. As concerns their distribution by gender, 79 (55.2%) were female and 64 (44.8%) were male. Grade II meningiomas were most commonly located at convexity 49.7% (n=71), followed by skull base in 30.8% (n=44) of the cases and parasagittal/falcine in 14.7% (n=21) of the patients. Conclusions. The most common localization of grade II meningiomas was convexity, followed by skull base, parasagittal/falcine and intraventricular areas. We have also noticed that convexity meningiomas are more frequent in women, unlike the other anatomical localizations in which the male-female ratio is almost equal. Therefore, further research is necessary to determine the role of embryological, anatomopathological and genetic factors in underlying the connection between meningioma grade and anatomical localization. INTRODUCTION Meningiomas makes up about one third of all primary central nervous system tumours, being the most common brain tumour in adults over the age of 35 (1), with an incidence that has increased in recent years (2, 3). As far as Romania is concerned, an increase in the number of intracranial meningiomas was noted in its North-Eastern region (where this research was conducted) over the 1990-2015 period (4). Although meningiomas are usually benign slow-growing tumours, their Keywords atypical meningioma, grade II WHO meningioma, meningiomas localization Corresponding author: Claudia Florida Costea "Grigore T. Popa" University of Medicine and Pharmacy Iași, Romania costea10@yahoo.com Copyright and usage. This is an Open Access article, distributed under the terms of the Creative Commons Attribution Non–Commercial No Derivatives License (https://creativecommons .org/licenses/by-nc-nd/4.0/) which permits non- commercial re-use, distribution, and reproduction in any medium, provided the original work is unaltered and is properly cited. The written permission of the Romanian Society of Neurosurgery must be obtained for commercial re-use or in order to create a derivative work. ISSN online 2344-4959 © Romanian Society of Neurosurgery First published September 2019 by London Academic Publishing www.lapub.co.uk http://www.lapub.co.uk/ 233 Anatomical localization of intracranial grade II meningiomas in North-Eastern Romania histological aggressiveness may classify them in grade II or III tumours, according to the WHO classification (5, 6). Whereas grade II meningiomas only made up 5-7% of all types of meningiomas before the 2007 WHO classification (7), they currently make up more that 20% of all meningiomas (7, 8, 9). Grade II meningiomas include three histological subtypes: atypical, the most common, and also chordoid and clear cell meningiomas, the occurrence rate of which is considerably lower (10). Among the multiple prognostic factors that can predict meningioma grade prior to tissue diagnosis (11, 12), several studies also found the anatomical localization (13, 14). Thus, several authors noticed the predisposition of grade II meningiomas for cerebral convexity (13, 15, 16) (Figure 1). FIGURE 1. Preoperative and postoperative axial T1-weighted images with contrast of an atypical meningioma (Professor Poeata’s personal collection) The goal of our research was to analyze grade II meningiomas distribution in North-Eastern Romania over a 25-year period (1990-2015). The patients underwent surgery in "Prof. Dr. N. Oblu" Emergency Clinical Hospital of Iasi, the advantage of this hospital being the fact that it services the whole of North- Eastern Romania, a region with a population of about 4 million inhabitants (17) (Figure 2). FIGURE 2. Preoperative coronal (A) and axial (B) T1-weighted images with contrast showing a left falcine meningioma. Postoperative images showing tumour bed after gross total resection (C) (Assoc. Professor Turliuc’s personal collection) MATERIAL AND METHODS We have evaluated 143 patients hospitalized in "Prof. Dr. N. Oblu" Emergency Clinical Hospital of Iași between 1990 and 2015, with histologically proven grade II meningiomas (atypical, clear cells and chordoid). Also, the histological samples have been reviewed according to the current WHO 2016 criteria (18). We have excluded all patients with type 2 neurofibromatosis (2 patients) and those for whom we were unable to collect full information about tumors (16 patients). The collected data included: gender, age, anatomical localization and histopatho- logical diagnosis (Table I). In order to confirm the anatomical localization of grade II meningiomas, the surgeon’s operative notes were taken into consideration. As concerns the intracranial localization of meningiomas, they were divided into four main categories: (1) convexity, (2) parasagittal/falcine, (3) skull base and (4) intraventricular. RESULTS Of all 143 patients with meningiomas, 79 (55.2%) were female patients and 64 (44.8%) were male 234 A.I. Cucu, Claudia Florida Costea, Mihaela Dana Turliuc et al. patients. The male: female ratio was 1:1.2. As concerns patients distribution on demographic groups, more than half of them were in the 50-69 year age group (58.1%, n=83). As for the distribution of meningiomas according to anatomical localiza- tion, they occurred mostly: 49.7% (n=71) at convex- ity, 30.8% (n=44) at skull base, 14.7% (n=21) in the p a r a s a g i t t a l / f a l c i n e a r e a a n d 4 . 9 % ( n = 7 ) intraventricular. Most meningiomas were atypical (94.4%, n=135), followed by clear cell meningiomas (4.2%, n=6) and only 1.4% (n=2) were chordoid. All patient charac teristics are s ho wn in Table I. Characteristics Grade II n (%) No. of patients 143 Gender female male 79 (55.2) 64 (44.8) Age groups (years) 20-29 30-39 40-49 50-59 60-69 70-79 80-89 3 (2.1) 9 (6.3) 23 (16.1) 42 (29.4) 41 (28.7) 22 (15.4) 3 (2.1) Tumor localization Convexity Skull base Parasagittal/falcine Intraventricular 71 (49.7) 44 (30.8) 21 (14.7) 7 (4.9) Histological subtypes Atypical meningioma Clear cell meningioma Chordoid meningioma 135 (94.4) 6 (4.2) 2 (1.4) TABLE 1. Characteristics of 143 patients with grade II meningioma DISCUSSION Our research revealed a predilection of grade II meningiomas for the convexity, as 49.7% (n=71) of them occurred in this area, which is consistent with similar studies (10, 14, 19, 20, 21, 22). Skull base meningiomas ranked second 30.8% (n=44), followed by the parasagittal/falcine and intraventricular localization (Table 1, Figure 3). The distribution of the anatomical localization of tumors on age groups was similar in both women and men. FIGURE 3. Incidence of Grade II meningiomas according to anatomical localization 235 Anatomical localization of intracranial grade II meningiomas in North-Eastern Romania Although previous studies have demonstrated a predilection of grade II meningiomas for cerebral convexity (13, 15, 16), a clear etiological connection between a particular meningioma grade and its anatomical localization could not be established. However, some authors consider that the histological grade of the tumor may be related to the meninges’ complex embryological origin, which has a variable neoplastic potential (23, 24, 25, 26). Among the first studies that demonstrated the predilection of grade II meningiomas for cerebral convexity were those conducted by Mahmood et al. and Maier et al. (27, 28). Also, Kane et al. later demonstrated that non-skull base tumors would have an increased risk for grade II meningiomas compared to skull base tumors (13). On the other hand, Zhou et al. noted that meningiomas located at the median line of the skull base are the least likely to be grade II or III (6), similar to other studies that have revealed that skull base meningiomas are more frequently meningothelial (29, 30) and are also lower grade at initial resection (15). This predilection of meningiomas for various anatomical localizations in the intracranial space could be explained by the distinct embryological origins of non-skull and skull- base dura (14, 15, 30, 31). In this respect, various authors have demonstrated that meninges around the brainstem would arise from cephalic mesoderm, whereas telencephalic meninges arise from neural crest cells (25, 29, 32, 33). This differential meningeal embryogenesis resulted in the predominance of one arachnoid cell type over the other location, which accounts for the aggressive behavior of some meningiomas as compared to others in some anatomical localizations (15). However, genomic studies have shed light on intracranial locations and mutational patterns, as well as on the potential embryonic cancer stem cell-like origin (34). In a study on 110 patients with incidentally discovered meningiomas, Hashimoto et al. also noticed that non-skull base meningiomas have a more aggressive behavior and that skull base meningiomas do not tend to grow when compared to non-skull base meningiomas (35). Moreover, even when these tumors grow, the growth rate was significantly lower in terms of annual growth rate and percentage (35). Also, the same authors demonstrated that 60% of the skull base incidental meningiomas had an exponential pattern of growth, unlike non-skull base incidental meningiomas characterized by a 33% growth percentage (35). In conclusion, the authors recommend non-skull base meningioma follow-up by magnetic resonance imaging at shorter intervals. The authors mention that the results must be interpreted as most meningiomas fit both exponential and linear patterns statistically (35). In 2003, the same authors suggested that a loss of 1p was shown to be significantly correlated with malignant progression of meningiomas, analyzing 72 grade II and III meningiomas, with fluorescence in situ hybridization and loss of heterozygosity analyses (35, 36). The authors also pointed out that skull base meningiomas had a significantly lower percentage of cells with 1p loss (20.31%) compared to non-skull base meningiomas (37.87%), suggesting that skull base tumors would have fewer genetic alterations and consequently would have less aggressive biological behavior (35). Similarly, Murphy et al. showed in their study that meningiomas originating at the convexity had more chromosomal abnormalities than those arise from skull base (37). In terms of histopathology, there have been studies that have shown its importance in the prediction of some types of meningiomas for certain intracranial localizations. Thus, McGovern et al., in a study of 216 patients with grade I, II and III meningiomas, claimed that grade I non-skull base meningiomas had a higher MIB-1 labeling index than grade I skull base meningiomas, suggesting that non- skull base tumors may have a more aggressive biology (16). As concerns their recurrence, the same author noted that non-skull base meningiomas, when they recur, have a higher WHO grades than skull base meningiomas (16). Also, in 2018, Turk et al. concluded in a study of 40 grade I and II meningiomas that the skull base group had significantly higher CD34 levels than the non-skull base group, suggesting that skull base meningiomas tend to have higher microvascular density and are better vascularized than non-skull base tumors (38). As regards the distribution of meningiomas on genders in the overall number of patients, we revealed a male: female ratio of 1:1.2, with a slight predominance in females, in agreement with other literature studies (14, 19, 39). On the other hand, whereas in the skull base, intraventricular and parasagittal/falcine localizations the male: female ratio was approximately 1:1, location at convexity level was dominated by women, with a male: female 236 A.I. Cucu, Claudia Florida Costea, Mihaela Dana Turliuc et al. ratio of 1:1.5 (43/28) (Figure 4). In order to justify this predominance of women, research has shown that grade I meningiomas have a high level of progesterone receptor expression relative to grade II and III meningiomas, which seem to have a lower frequency of estrogen and androgen receptors (13, 40, 41, 42), which means close male-female ratios. On the other hand, Morokoff et al. in a study of 163 convexity meningiomas (grades I, II and III) noted a prevalence of the female sex, with a male: female ratio of 1:2.7 (43). In higher-grade meningiomas, Morokoff et al. found a male: female ratio of 1:1, much lower than our ratio of 1:1.5. FIGURE 4. Incidence of grade II meningioma according to gender With regard to the distribution of histological subtypes of grade II meningiomas, atypical meningiomas prevailed in our research (94.4%), followed by clear cell and chordoid meningiomas in a much lower percentage, as there are rare types of tumors (Table 1). Of all grade II meningiomas, atypical meningiomas are the most common, their percentage increasing to 20-30% of all meningiomas after the introduction of the WHO classification in 2000 and 2007 (2, 8, 9). Like grade I or III meningiomas, atypical meningiomas may develop anywhere in the intracranial space, with some studies reporting a higher frequency of atypical meningiomas at the level of cerebral convexity (8, 27, 44, 45). Clear cell meningioma is a rare disorder, as it makes up less than 1% of all meningiomas, and English-language literature reports 218 intracranial tumors (46). This percentage is also low in our research, with an incidence rate of this type of meningioma only 4.2% (n=6) over the 25-year period (Table I). Whereas previous studies revealed that the most common localization for clear cell meningioma was the cerebellopontine angle (47, 48, 49), all clear cell meningiomas in our group were located in the parasagittal/falcine area (n = 6). From this point of view, the results of the studies differ from each other: some studies show that the most affected location is convexity (46), whereas others point to skull base (50), particularly cerebellopontine angle, parasagittal tumors having lower occurrence rates (47). Chordoid meningiomas are also rare types of meningiomas, as only a little more than 100 cases are reported in literature (51, 52, 53, 54, 55, 56). Rare neoplasia with a unique chordoid appearance, chordoid meningioma has a predilection for the supratentorial localization (1, 57), similar to our study in which the two chordoid meningiomas had parasagittal/falcine localization. CONCLUSIONS Our study has shown a predominance of grade II meningiomas for cerebral convexity, which is the most common location in the intracranial space, followed by the skull base, parasagittal/falcine and intraventricular locations. We also noticed that convexity meningiomas predominate especially in women. Further research is needed to highlight the role of genetic, embryological and anatomopathological factors in highlighting the 237 Anatomical localization of intracranial grade II meningiomas in North-Eastern Romania connection between meningioma grade and anatomical localization REFERENCES 1. Louis DN, Scheitauer BW, Budka H, von Deimling A, Kepes JJ. Meningiomas. In: Kleihues P, Cavenee WK (eds). Pathology and Genetics of Tumors of the Nervous System. Lyon: IARC Press, 2000. 2. Willis J, Smith C, Ironside JW, et al. The accuracy of meningioma grading: a 10-year retrospective audit. Neuropathol Appl Neurobiol. 2005; 31:141-149. 3. Cucu AI, Turliuc DM, Costea CF, et al. Pathways of metastatic spread in meningiomas. Romanian Neurosurgery. 2019; 33(1):12-16. 4. Cucu AI, Costea CF, Carauleanu A, et al. Meningiomas related to the Chernobyl irradiation disaster in North- Eastern Romania between 1990 and 2015. Revista de Chimie Bucharest. 2018; 69:1562-1565. 5. Aboukais R, Baroncini M, Zairi F, et al. Early postoperative radiotherapy improves progression free survival in patients with grade 2 meningioma. Acta Neurochir (Wien). 2013; 155(8):1385-1390; discussion 1390. 6. Zhou P, Ma W, Yin S, et al. Three risk factors for WHO grade II and III meningiomas: a study of 1737 cases from a single center. Neurol India. 2013; 61:40-44. 7. Perry A, Louis DN, Scheithauer BW, et al. Meningiomas. In: Louis DN, Ohgaki H, Wiestler OD, Cavenee WK (eds) WHO classification of tumours of the central nervous system. Lyon: IARC Press, 2007. 8. Pasquier D, Bijmolt S, Veninga T, et al. Atypical and malignant meningioma: outcome and prognostic factors in 119 irradiated patients a multicenter, retrospective study of the rare cancer network. Int J Radiat Oncol Biol Phys. 2008; 71:1388-1393. 9. Pearson BE, Markert JM, Fisher WS, et al. Hitting a moving target: evolution of a treatment paradigm for atypical meningiomas amid changing diagnostic criteria. Neurosurg Focus. 2008; 24:E3. 10. Durand A, Labrousse F, Jouvet A, et al. WHO grade II and III meningiomas: a study of prognostic factors. J Neurooncol. 2009; 95(3):367-375. 11. Cucu AI, Costea CF, Poeata I, et al. Prognostic factors in atypical meningioma. Rom Neurosurg. 2017; 31(2):165- 171. 12. Cucu AI, Turliuc MD, Carauleanu A, et al. Chemical aspects of peritumoral cerebral edema in atypical meningiomas. Rev Chim (Bucharest). 2018; 69:2804-2807. 13. Kane AJ, Sughrue ME, Rutkowski MJ, et al. Anatomic location is a risk factor for atypical and malignant meningiomas. Cancer. 2011; 117(6):1272-1278. 14. Cucu AI, Costea CF, Poeata I, et al. Anatomical localization of atypical meningiomas: our experience on 81 patients. Rev Med Chir Soc Med Nat Iasi. 2018; 122:744-752. 15. Sade B, Chahlavi A, Krishnaney A, et al. World Health Organization Grades II and III meningiomas are rare in the cranial base and spine. Neurosurgery. 2007; 61(6):1194- 1198. 16. McGovern SL, Aldape KD, Munsell MF, et al. A comparison of World Health Organization tumor grades at recurrence in patients with non-skull base and skull base menin- giomas. J Neurosurg. 2010; 112(5):925-933. 17. www.recensamantromania.ro – the official site of the Romanian National Institute of Statistics. 18. Louis DN, Perry A, Reifenberger G, et al. The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. Acta Neuropathol. 2016; 131(6):803-820. 19. Zaher A, Abdelbari Mattar M, et al. Atypical meningioma: a study of prognostic factors. World Neurosurg. 2013; 80(5):549-553. 20. Nanda A, Bir SC, Konar S, et al. Outcome of resection of WHO Grade II menin-gioma and correlation of pathological and radiological predictive factors for recurrence. J Clin Neuro-sci. 2016; 31:112-121. 21. Budohoski KP, Clerkin J, Millward CP, et al. Predictors of early progression of surgically treated atypical meningiomas. Acta Neurochir (Wien). 2018; 160(9):1813- 1822. 22. Champeaux C, Houston D, Dunn L. Atypical meningioma. A study on recurrence and disease-specific survival. Neurochirurgie. 2017; 63(4):273-281. 23. Backer-Grøndahl T, Moen BH, Torp SH. The histopathological spectrum of human meningiomas. Int J Clin Exp Pathol. 2012; 5(3):231-242. 24. O'Rahilly R, Muller F. The meninges in human development. J Neuropathol Exp Neurol. 1986; 45:588-608. 25. Catala M. Embryonic and fetal development of structures associated with the cerebro-spinal fluid in man and other species. Part I: The ventricular system, meninges and choroid plexuses. Arch Anat Cy-tol Pathol. 1998; 46:153- 169. 26. Rutkowski MJ, Jian BJ, Bloch O, et al. Intracranial hemangiopericytoma: clinical experience and treatment considerations in a modern series of 40 adult patients. Cancer. 2012; 118(6):1628-1636. 27. Mahmood A, Caccamo DV, Tomecek FJ, et al. Atypical and malignant meningiomas: a clini-copathological review. Neurosurgery. 1993; 33:955-963. 28. Maier H, Ofner D, Hittmair A, et al. Classic, atypical, and anaplastic meningioma: three histopathological subtypes of clinical relevance. J Neurosurg. 1992; 77(4):616-623. 238 A.I. Cucu, Claudia Florida Costea, Mihaela Dana Turliuc et al. 29. Kros J, de Greve K, van Tilborg A, et al. NF2 status of meningiomas is associated with tumor localization and histology. J Pathol. 2001; 194:367-372. 30. Lee JH, Sade B, Choi E, et al. Meningothelioma as the predominant histological subtype of midline skull base and spinal meningioma. J Neurosurg. 2006; 105(1):60-64. 31. Kepes JJ. Presidential address: the histopathology of meningiomas. A reflection of origins and ex-pected behavior? J Neuropathol Exp Neurol. 1986; 45(2):95-107. 32. Russell D, Rubenstein L. Pathology of Tumours of the Central Nervous System. Baltimore: Williams and Wilkins, 1989. 33. Perry A, Gutmann DH, Reifenberger G. Molecular pathogenesis of meningiomas. J Neurooncol. 2004; 70(2):183-202. 34. Karsy M, Azab MA, Abou-Al-Shaar H, et al. Clinical potential of meningioma genomic insights: a practical review for neurosurgeons. Neurosurg Focus. 2018; 44(6):E10. 35. Hashimoto N, Rabo CS, Okita Y, et al. Slower growth of skull base meningiomas compared with non-skull base meningiomas based on volumetric and biological studies. J Neurosurg. 2012; 116(3):574-580. 36. Murakami M, Hashimoto N, Takahashi Y, et al. A consistent region of deletion on 1p36 in meningiomas: identification and relation to malignant progression. Cancer Genet Cytogenet. 2003; 140:99-106. 37. Murphy M, Pykett MJ, Harnish P, et al. Identification and characterization of genes differentially expressed in meningiomas. Cell Growth Differ. 1993; 4:715-722. 38. Turk O, Asik M, Batur S, et al. Correlation of preoperative radiological evaluation of skull and non-skull base meningiomas with clinical and surgical data. Turk Neurosurg. 2018; in press. 39. Barthélemy E, Loewenstern J, Konuthula N, et al. Primary management of atypical meningioma: treatment patterns and survival outcomes by patient age. J Cancer Res Clin Oncol. 2018; 144(5):969-978. 40. Korhonen K, Salminen T, Raitanen J, et al. Female predominance in meningiomas can not be explained by differences in progesterone, estrogen, or androgen receptor expression. J Neurooncol. 2006; 80:1-7. 41. Whittle IR, Foo MS, Besser M, et al. Progesterone and oestrogen receptors in meningiomas: biochemical and clinicopathological considerations. Aust N Z J Surg. 1984; 54:325-330. 42. Wolfsberger S, Doostkam S, Boecher-Schwarz HG, et al. Progesterone-receptor index in meningiomas: correlation with clinico-pathological parameters and review of the literature. Neurosurg Rev. 2004; 27:238-245. 43. Morokoff AP, Zauberman J, Black PM. Surgery for convexity meningiomas. Neurosurgery. 2008; 63(3):427-33; discussion 433-434. 44. Modha A, Gutin PH. Diagnosis and treatment of atypical and anaplastic meningiomas: a review. Neurosurgery. 2005; 57(3):538-550. 45. Hammouche S, Clark S, Wong AH, et al. Long-term survival analysis of atypical meningiomas: survival rates, prognostic factors, operative and radiotherapy treatment. Acta Neurochir (Wien). 2014; 156(8):1475-1481. 46. Li P, Yang Z, Wang Z, et al. Clinical features of clear cell meningioma: a retrospective study of 36 cases among 10,529 patients in a single institution. Acta Neurochir (Wien). 2016; 158(1):67-76. 47. Tao X, Dong J, Hou Z, et al. Clinical features, treatment, and prognostic factors of 56 intracranial and intraspinal clear cell meningiomas. World Neurosurg. 2018; 111:e880-e887. 48. Chen H, Li XM, Chen YC, et al. Intracranial clear cell meningioma: a clinicopathologic study of 15 cases. Acta Neurochir (Wien). 2011; 153 (9):1769–1780. 49. Wang XQ, Huang MZ, Zhang H, et al. Clear cell meningioma: clinical features, CT, and MR imaging findings in 23 patients. J. Comput Assist Tomo. 2014; 38(2):200-208. 50. Zhang H, Ma L, Wang YB, et al. Intracranial clear cell meningiomas: study on clinical features and predictors of recurrence. World Neurosurg. 2017; 97:693-700. 51. Kozler P, Benes V, Netuka D, et al. Chordoid meningioma: presentation of two case reports, review of the literature, and plea for data standardisation. J Neurooncol. 2008; 88:115-120. 52. Kepes JJ, Chen WY, Connors MH, et al. “Chordoid” meningeal tumors in young individuals with peritumoral lymphoplasmacellular infiltrates causing systemic manifestations of the Castleman syndrome. A report of seven cases. Cancer. 1988; 62:391-406. 53. Lin JW, Ho JT, Lin YJ, et al. Chordoid meningioma: a clinicopathologic study of 11 cases at a single institution. J Neurooncol. 2010; 100:465-473. 54. Epari S, Sharma MC, Sarkar C, et al. Chordoid meningioma, an uncommonvariant of meningioma: a clinicopathologic study of 12 cases. J Neurooncol. 2006; 78:263-269. 55. Couce ME, Aker FV, Scheithauer BW. Chordoid meningioma: a clinicopathologic study of 42 cases. Am J Surg Pathol. 2000; 24:899-905. 56. Zhu HD, Chen H, Xie Q, et al. Chordoid meningioma: a retrospective study of 17 cases at a single institution. Chin Med J. 2013; 126:789-791. 57. Tena-Suck ML, Collado-Ortìz MA, Salinas-Lara C, et al. Chordoid meningioma: a report of ten cases. J Neurooncol. 2010; 99(1):41-48.