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NI FEATURE: PATHOLOGY PANORAMA - ORIGINAL ARTICLE
Year : 2018  |  Volume : 66  |  Issue : 1  |  Page : 156--160

Chromosomal aberrations in chordoid meningioma – An analysis

Harsha Sugur1, Arun H Shastry2, Nishant Sadashiva3, Dwarakanath Srinivas3, Vani Santosh1, Sampath Somanna3,  
1 Department of Neuropathology, National Institute of Mental Health and Neuroscience, Bengaluru, Karnataka, India
2 Department of Clinical Neuroscience, National Institute of Mental Health and Neuroscience, Bengaluru, Karnataka, India
3 Department of Neurosurgery, National Institute of Mental Health and Neuroscience, Bengaluru, Karnataka, India

Correspondence Address:
Dr. Dwarakanath Srinivas
Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka
India

Abstract

Introduction: Chordoid meningiomas (CMs) are a rare subgroup of tumors, accounting for approximately 0.5% of all meningiomas. These tumors correspond to World Health Organization (WHO) Grade II lesions and behave aggressively, with an increased likelihood of recurrence. There are only two studies that have described the genetic alterations in CMs. While a majority of meningiomas are known to have deletion at many chromosomal loci such as 22q, 18p, 14q, and 1p, which are found to be associated with initiation, progression, and malignancy of these tumors, these have not yet been studied in CMs. Thus, our aim was to evaluate the status of these four chromosomal aberrations in CMs and correlate the findings with the clinical outcome of patients. Materials and Methods: A total of 15 cases of CM operated over a period of 12 years from 2001 to 2013 were analyzed. The archival paraffin blocks were retrieved and sections were subjected to locus-specific fluorescent in situ hybridization (FISH) using 22q12.2, 18p11.3, 14q32.2, and 1p32.3 probes. Immunohistochemistry (IHC) was done on all cases using MIB-1, vimentin, glial fibrillary acidic protein (GFAP), and epithelial membrane antigen (EMA) antibodies. Results: All cases had characteristic features of CM, and were positive for EMA and vimentin and negative for GFAP. The mean labeling index for MIB-1 was 2.7 ± 0.8%. Of the 15 cases, 5 cases showed recurrence with a median follow-up period of 28 months. Patients who underwent Simpson's grade I excision did not show any relapse of the tumor. Of the 5 recurrent cases, 4 had complete deletion of all four chromosomal loci. Among the 10 nonrecurrent cases, 9 (90%) showed either partial deletion or an intact status. Conclusions: This is the first study to evaluate the combined chromosomal status of 22q, 18p, 14q, and 1p in CMs. Our study shows that there was a higher propensity of recurrence in tumors, even with complete excision, with complete deletion in all four chromosomal loci.



How to cite this article:
Sugur H, Shastry AH, Sadashiva N, Srinivas D, Santosh V, Somanna S. Chromosomal aberrations in chordoid meningioma – An analysis.Neurol India 2018;66:156-160


How to cite this URL:
Sugur H, Shastry AH, Sadashiva N, Srinivas D, Santosh V, Somanna S. Chromosomal aberrations in chordoid meningioma – An analysis. Neurol India [serial online] 2018 [cited 2019 Jun 26 ];66:156-160
Available from: http://www.neurologyindia.com/text.asp?2018/66/1/156/222808


Full Text



Chordoid meningiomas (CMs), WHO grade II tumors, are uncommon variants of meningioma.[1] CMs are typically large, supratentorial,[1],[2] dural-based tumors which behave aggressively when compared to other grade II tumors.[1] They have striking features such as cords or trabeculae of eosinophil and vacuolated cells in an abundant mucoid matrix background.[3] The tumor commonly shows peritumoral reactive lymphoplasma cellular infiltration.[4],[5] They are associated with a poor prognosis and exhibit a very high rate of recurrence of approximately 42%.[1] Recurrence is generally predicted based on the surgical dissection, the percentage of chordoid element, and proliferation index. Approximately 75% of patients show recurrence within a period of 1 year when only subtotal resection is achieved,[6] thereby increasing the need for adjuvant therapy, i.e., radiotherapy or chemotherapy, particularly when Simpson grade I resection is not achieved.[7] Many studies suggest that high proliferation indices (KI-67 levels) of >4% MIB levels are predictors of recurrence.[1],[8] Chordoid elements range from 10 to 100% in these tumors,[1] and it is found that tumors with 50% or more of chordoid elements help in determining recurrence.[9]

There have been only two studies on chromosomal aberrations in CM in the available literature. One on chromosomal alteration of primary and recurrent CM evaluated the loci MYCN, ERBB4, CDH1, ABR, ERBB2, and NF2 probes [10] and showed that there is some level of alteration in genes such as NF2, MYCN, ABR, and ERBB2 among primary and recurrent CMs.[10] Another study showed an unbalanced translocation of t(1;3)(p12-13;q11) as a unique feature of CM.[11],[12] Most frequent chromosomal aberration in meningiomas such as deletions of chromosomes 1, 3, 6, 9, 10, 14, 18, and 22, which are responsible for the genesis and malignancy, have not been studied in CM, except for 22q. Thus, our aim was to study the chromosomal aberrations of extensively studied gene loci such as 22q, 18p, 14q, and 1p and to correlate the findings with the clinical outcome of patients.

 Materials and Methods



This study was conducted at the National Institute of Mental Health and Neurosciences (NIMHANS), Bengaluru. A total of 25 intracranial CMs were operated from 2001 to 2013. The paraffin blocks were retrieved and the neuropathologist reviewed all the cases. Ten cases were excluded either due to inadequate tissue or reclassification into other subtypes. Clinical, demographic, and follow-up data were collected for patients. The institutional ethics committee approved the study. The mean age of patients was 32 years. The median follow up duration was 28 months with the maximum follow up duration being 151 months.

Fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) was conducted on formalin-fixed paraffin-embedded (FFPE) sections. 4-μm thick tumor tissues were collected on silane-coated slides. Locus-specific single-color probes were used for performing the assay. The genes studied included Neurofibromin 2(NF 2) [Empire Genomics, Buffalo, NY 22q12.2], DAL-1 or 4.1B gene or Erythrocyte Membrane Protein Band 4.1- Like 3 (EPB41L3) [Empire Genomics, Buffalo, NY, 18p11.3], Maternally Expressed Gene 3 (MEG-3) [Empire Genomics, Buffalo, NY, 14q32.2], and Cyclin-Dependent Kinase Inhibitor 2C (CDKN2C) [Empire Genomics, Buffalo, NY, 1p32.3]. After paraffin pretreatment and protease digestion, the probe was applied to the sections. Simultaneous probe/specimen denaturation at 80°C for 3 min and hybridization at 37°C for 20 h was performed in a ThermoBrite™ hybridization chamber (Vysis Instrumentation, Abbott Laboratories, Illinois, USA). The posthybridization process included washing in 2× SSC (saline sodium citrate buffer) with 0.3% NP-40 (nonidet P-40) for 5 min at room temperature and 2× SSC with 0.3% NP-40 at 73°C for 1 min. Nuclei were counterstained with DAPI (1000 ng DAPI [4',6-diamidino-2-phenylindole]/ml in antifade mounting solution, Vysis). The sections were studied with a trinocular research fluorescent microscope (Olympus Model: BX51; Olympus, Tokyo) equipped with a set of appropriate filters. Signals were counted for 100 nonoverlapping nuclei. Every case was examined and the abnormalities were divided based on the regional distributions of chromosomal aberrations (i.e. homogenous or heterogeneous) and the type of deletion (homozygous or heterozygous). Thus, the cases were categorized into three groups: Completely deleted (homogenous homozygous/heterozygous deletion), partially deleted (heterogeneous heterozygous deletion), retained (intact or nondeleted status).

Cut-offs for deletions and aberrations were based on the frequencies of signals for the same probes in nonneoplastic brain control tissues. If the FISH signals were too weak to count, the hybridization was considered noninformative.

Immunohistochemistry

Paraffin sections (4 μm) from the tissue were collected on silane-coated slides, and immunohistochemistry for the protein expression of KI-67 (Biogenex-MIB-1, Monoclonal Mouse, 1:90), EMA (Biogenex, RTU), vimentin (Biogenex, Mouse, 1:150) and GFAP (Biogenex, Mouse, 1:200) was performed. Tumor tissues that previously showed overexpression served as positive controls and were included in each batch of staining. Antigen retrieval was done by heat treatment of the deparaffinized sections in Tris–EDTA buffer (pH 8.9). After the initial processing steps, sections were incubated overnight with the primary antibody at 4°C. This was followed by incubation with the linked streptavidin-biotinylated secondary antibody and then with the supersensitive nonbiotin horseradish peroxidase detection system (Nucleus Technologies, MACH1 Universal HRP-Polymer Detection, 110 ml). For MIB-1, the labeling index (LI) was expressed as a percentage of cells that showed intense positive staining among the total number of cells counted.

 Results



Demographic details

A total of 25 patients were operated. Out of these, two cases were eliminated as they were spinal CMs, six were reclassified as other varieties of tumors, and two were not included on account of inadequate tissue. The mean age of patients was 32 years (minimum age = 9 years, maximum age = 50 years) and male to female ratio was 1:2.75. There were 14 skull vault and 1 basal CM. Simpson's grade (SG) 1 resection was performed in four cases out of 15 patients. SG2, SG3, SG4, and SG5 excision was performed in 5/15, 4/15, 1/15, and 1/15 cases, respectively. The median follow up was 28 months, ranging from 3 to 151 months. During this follow-up period, recurrence was noted in five patients, whereas 10 showed no clinical evidence of recurrence. Of the five patients with a recurrence, only three underwent surgery for the second time.

Immunohistochemistry

All cases were variably positive for EMA and showed strong positive staining for vimentin, but were completely negative for GFAP, in support of the diagnosis. The MIB labeling ranged from 0.5 to 10% with a mean of 2.7%. Representative images of histology and IHC for MIB-1, EMA, and vimentin for CMs are shown in [Figure 1].{Figure 1}

Fluorescence in situ hybridization

All samples showed adequate FISH efficiency. All the cases (n = 15) showed either complete or partial deletion at 22q, 14q, and 1p loci. For 18p loci, two cases showed retention status whereas the remaining cases showed either a partial deletion or a complete deletion status. The frequencies of chromosomal aberrations are shown in [Table 1] and representative images for these are depicted in [Figure 2].{Figure 2}{Table 1}

Recurrence

In the present cohort, only 33% of the cases had tumor recurrence on a maximum follow-up of 12 years. None among the four patients who underwent Simpson's grade I resection showed a recurrence. Interestingly, in our study, proliferative index (MIB1 labeling) was low (0.6 ± 0.22) in the recurrent sample when compared with the nonrecurrent (3.75 ± 4.1) samples. 80% (4/5) of the recurrent cases showed complete deletion on all four chromosomal loci whereas 90% of the cases (9/10), where the tumor did not recur, had either partial deletion or an intact chromosomal status. The contrast between recurrent and nonrecurrent patients is given in [Table 2].{Table 2}

 Discussion



CMs are commonly grouped according to their grade of malignancy; however, these tumors behave much more aggressively when compared with other WHO grade II meningiomas. Therefore, it is important to study the tumor specific alterations involved in their genesis and evolution.

These tumors have poorer prognosis and a higher recurrence rate of approximately 42%.[1] In general, factors influencing recurrence in meningiomas include unfavorable tumor localization, incomplete surgical dissection, and high tumor cell proliferation, among others. Specifically, in CM, an additional factor responsible for recurrence is the extent of chordoid elements. It was observed that 85% of tumors relapsed when chordoid elements were more than 50%.[4],[13] As our cohort (n = 15) included cases which had predominantly chordoid areas (>50%), such a comparison was not attempted. Studies on CMs have shown that MIB-1 level is usually low in these tumors ranging from 1 to 2%.[14],[15] The mean MIB labeling index (LI) in our study was 2.7 ± 0.8%. We noted that the MIB-1 labeling index did not correlate with recurrence in this cohort of CMs. The mean MIB-1 LI in recurrent cases was very low, about 0.6% (n = 5), ranging from 0.5 to 1%, and most of the nonrecurrent cases had a higher mean (3.7%). Even though there have been studies that correlate high MIB-1 levels with recurrence, similar to our observation, there are a few others that have shown that MIB-1 is not an accurate indicator for predicting recurrence.[15]

Recurrence in meningiomas depends primarily on the extent of surgical removal of the tumor. Higher the extent of removal, lesser is the chance of relapse of the tumor.[7],[16] We also found that patients who underwent Simpson's grade I excision (100%) did not have tumor recurrence. In our study, 57% of the patients had recurrence when the tumor was subtotally resected, which is slightly less when compared with the recurrence rate of 92% reported in the previous studies.[1] We studied the chromosomal aberration in these tumors including commonly studied markers in meningiomas such as 22q, 18p, 14q, and 1p, because only two studies have dealt with chromosomal alterations in these tumors. 22q aberration is a primordial event for the genesis of meningiomas and is deleted in 40–70% of meningiomas.[17] 18p loss was detected in sporadic meningiomas, affecting more than 70% of tumors regardless of their histological grade.[18] Loss of 1p represents the most frequent genetic alteration secondary to chromosome 22q loss and is found to be associated with tumor progression.[18] Chromosome 14q represents the third-most frequently detected abnormality, seen in 100% of grade III meningiomas.[19] We found that all cases had either complete or partial deletion status for 22q, 14q, and 1p chromosomal loci. NF2 gene locus was found to be deleted (either complete or partially) in all cases, which is contradictory to what was previously reported in cases where tumors showed NF2 amplification status and had recurred.[10]

Interestingly, we found that 80% (4/5) of patients with recurrent tumors had complete deletions on all four chromosomal loci. Only one tumor of the five which recurred showed partial deletion, but in this case, the grade of excision was inadequate (Simpson's grade IV), which could be responsible for the recurrence. The nonrecurrent, 90% (9/10) cases had either a partially deleted or a retained status for the respective loci. Only one nonrecurrent case had complete deletion, and this patient is on a regular follow-up. We have noted that complete deletion of all four genes might be a unique characteristic of recurrent CM. This finding is contrary to our previous study on atypical meningiomas, where complete deletion of all four genes was not associated with recurrence.[20] Co-deletion on all four loci in CMs can now be validated on further studies to project it as a unique feature for CMs, as well as to highlight its utility as a method to predict recurrence.

 Conclusion



This is the first study to evaluate the chromosomal status of 22q, 18p, 14q, and 1p in CMs. Our study showed that CMs routinely harbor either complete or partial deletion at 22q, 14q, and 1p loci. MIB-1 LI is not a reliable indicator of recurrence in CMs. CMs that showed recurrence had complete deletion of all four loci in sharp contrast to tumors which did not recur. In view of lack of MIB1 labeling to identify recurrence in CMs, evaluation of chromosomal status for the abovementioned markers serves as a promising adjunct to the extent of surgical resection in predicting tumor recurrence.

Acknowledgements

We acknowledge the contributions of Mr. Chandrashekhar and Mr. Tilak toward tumor tissue processing and preparation of slides for immunohistochemical and FISH studies. The Department of Science and Technology (The Science and Engineering Research Board: SERB), New Delhi, is acknowledged for provision of grants for conducting the current study.

The manuscript was presented as a poster at the 7th Annual Conference of the Indian Society for Neurooncology, ISNOCON-2015, Kochi, Kerala, in March 2015.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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