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ORIGINAL ARTICLE
Year : 2012  |  Volume : 60  |  Issue : 1  |  Page : 50-54

Does bony hyperostosis in intracranial meningioma signify tumor invasion? A radio-pathologic study


1 Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India
2 Department of Neuropathology, All India Institute of Medical Sciences, New Delhi, India

Date of Submission10-Sep-2011
Date of Decision01-Oct-2011
Date of Acceptance28-Nov-2011
Date of Web Publication7-Mar-2012

Correspondence Address:
Deepak Agrawal
Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi - 110 029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.93589

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 » Abstract 

Background: While operating intracranial meningiomas, neurosurgeons commonly drill the hyperostotic bone and put the bone flap back. Objective: To determine whether bony changes seen in meningioma are due to tumor invasion or reactionary changes. Materials and Methods: This prospective study, conducted over 10 months (October 2010- July 2011) included consecutive patients with intracranial meningiomas. Preoperatively, computed tomography (CT) was done in all patients and reviewed by two neurosurgeons for associated bony hyperostosis. During surgery, a piece of bone showing hyperostosis was taken for histopathological evaluation for tumor invasion. In absence of hyperostosis, the bone sample was taken from the bone in contact with the dural attachment of the tumor. Results: This study included 40 consecutive patients who underwent resection for intracranial meningiomas. Radiological evidence of hyperostosis was present in 30 (75%) patients. On histopathological examination, tumor invasion of the bone was seen in eight (20%) patients. These included seven patients who demonstrated hyperostosis and one patient without hyperostosis. Convexity meningiomas (n=12) showed the highest rate of bony invasion (33.3%). Conclusions: A significant number of patients with radiological hyperostosis have tumor invasion of the bone. The authors recommend that one should remove the bone (flap) whenever possible in order to achieve total excision of the tumor and use synthetic material to cover the defect.


Keywords: Bony hyperostosis, histopathology, meningioma, radiology, tumor invasion


How to cite this article:
Goyal N, Kakkar A, Sarkar C, Agrawal D. Does bony hyperostosis in intracranial meningioma signify tumor invasion? A radio-pathologic study. Neurol India 2012;60:50-4

How to cite this URL:
Goyal N, Kakkar A, Sarkar C, Agrawal D. Does bony hyperostosis in intracranial meningioma signify tumor invasion? A radio-pathologic study. Neurol India [serial online] 2012 [cited 2019 Aug 25];60:50-4. Available from: http://www.neurologyindia.com/text.asp?2012/60/1/50/93589



 » Introduction Top


The association between meningioma and hyperostosis was first described by Brissaud and Lereboullet in 1903. [1] However, the cause of hyperostosis has remained controversial. It has been hypothesized by several authors that hyperostosis may be a manifestation of tumor invasion. [2],[3],[4],[5],[6],[7],[8],[9],[10] However, some believe that these bony changes represent nothing else but reactionary changes. [2],[5],[6],[8],[9],[11],[12],[13],[14],[15],[16],[17],[18] As a common practice, neurosurgeons drill the hyperostotic bone and replace the bone flap in cases of intracranial meningiomas. This study aims at determining whether the bony changes seen in meningioma can be attributed to tumor invasion and consequently leaving the bone flap in situ may be the same as leaving a part of the tumor behind.


 » Materials and Methods Top


This prospective study included consecutive patients with a preoperative diagnosis of intracranial meningiomas who were operated between October 2010 and July 2011. Two neurosurgeons individually examined the preoperative magnetic resonance imaging (MRI) and computed tomography (CT) scans to assess for bony thickening overlying the tumor. Hyperostosis was defined as bony thickening in opposition to the tumor as compared to the adjoining bone. It was considered to be present if there was consensus among the two surgeons. The meningiomas were classified according to their location. During surgery, a piece of bone showing hyperostosis (in proximity to the tumor) was taken for histopathological evaluation for tumor invasion along with the tumor tissue. In absence of hyperostosis, the bone sample was taken from the bone in contact with the dural attachment of the tumor. The tumor tissue was processed routinely, while the bone was decalcified and then processed. Hematoxylin and eosin-stained slides of tumor tissue and the bone sample were examined by two neuropathologists. Immunohistochemistry was performed on the tumor tissue when required. The tumor tissue was assessed for tumor grade and type according to the World Health Organization (WHO) 2007 classification along with MIB-1 Labeling Index. The bone sample was screened for any evidence of tumor invasion.

Descriptive statistics including mean and frequency distributions were calculated for all variables, using SPSS software Version 15. Categorized data was analyzed by Chi-Square/Fischer Exact test. P value <0.05 was considered as the level of statistical significance.


 » Results Top


A total of 58 patients were initially enrolled in the study. On histopathology, nine of these patients were diagnosed to have lesions other than meningioma and were therefore excluded from the study. Of the 49 patients, nine were further excluded as the skull bone was not sampled from the representative area. The remaining 40 meningiomas were included in this prospective study.

Of the 40 patients included, 18 were males and 22 were females (ratio 0.8: 1). The median age of the patients at the time of surgery was 45.5 years (range 20-65 years; mean 44.3 ± 11.9 years) [Table 1]. Convexity meningiomas were most common (12 cases), followed by parasagittal and peritorcular (10 cases) and sphenoid wing meningiomas (10 cases). The others were falcine (four cases), tentorial (two cases) and one case each of optic nerve sheath meningioma and olfactory groove meningioma [Table 1]. Radiological evidence of hyperostosis was present in 30 (75%) patients [Table 2], [Figure 1]. In all these cases, the hyperostosis was confirmed intra-operatively.
Figure 1: Flowchart showing the histological results of bone biopsy in study patients

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Table 1: Radiological and histopathological features of meningiomas

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Table 2: Comparison of tumor location with hyperostosis and invasion into bone

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On histopathological examination, 36 cases belonged to WHO Grade I and four cases were WHO Grade II. Transitional meningiomas were most common (19 cases; 47.5%). MIB-1 labeling index ranged from 1 to 15% (mean = 3.5) [Table 1]. Tumor invasion into the bone was seen in eight (20%) of the 40 cases. These included seven which demonstrated hyperostosis and one without hyperostosis [Figure 1],[Figure 2] and [Figure 3], [Table 1]. No significant correlation was noted between hyperostosis and tumor invasion of the bone (P=0.65). Convexity meningiomas (n=12) showed the highest rate of bone invasion (33.3%) (P=0.21). The other cases showing tumor invasion into the bone were located in the sphenoid wing (two cases), parasagittal region (one case) and in the falx (one case) [Table 2]. Two cases of convexity meningioma did not show hyperostotic changes on radiology. However, on histopathology, one case (in which bone was biopsied from under the dural attachment) showed tumor invasion of the bone. Tumor invasion of the bone was present in three cases of meningothelial meningiomas (3 out of 8 cases; 37.5%) (P=0.32) and five cases of transitional meningiomas (5 out of 19 cases; 26.3%) [Table 1]. Tumor invasion of the bone did not show any significant correlation with WHO grade and MIB- 1 labeling index in our study.
Figure 2: Preoperative T1 sagittal (a) and coronal (b) images of contrast-enhanced MRI brain showing two well-defined lesions in the left anterior falcine region with moderate contrast enhancement. The bone overlying the larger lesion is increased in thickness, as seen on CT images (c). Photomicrograph of the tumor showing features of a meningothelial meningioma (WHO Grade I) with psammoma bodies (arrow) (original magnification, 100×) (d). Photomicrograph of bone biopsy showing the tumor infiltrating between bony trabeculae (original magnification, 100×) (e)

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Figure 3: Preoperative T1 contrast axial (a) and coronal (b) sections of MRI brain showing a lateral sphenoid wing meningioma with contrast enhancement and dural tail. Contrast CT head (c) showing abundant hyperostosis of the temporal bone and the lateral sphenoid wing; 100× (d) and 200× (e) magnification photomicrographs of the same patient showing a transitional meningioma (WHO Grade I) infiltrating between bony trabeculae and causing destruction of the underlying bone

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 » Discussion Top


The association between meningioma and hyperostosis is well known. [19] Hyperostosis is seen in 25-49% of meningiomas [16],[20],[21],[22] and was present in 75% of cases of meningioma studied in this series. The high incidence in our series may be due to inclusion of a greater number of meningomas involving the convexities and sphenoid wing, which are known to be associated more frequently with hyperostosis. [20],[23] In our study, we found that the maximum number of cases showing hyperostosis were convexity and sphenoid wing meningiomas.

The cause of hyperostosis in meningioma has long been a matter of debate. There are various hypotheses which aim at explaining this phenomenon including preceding trauma, [15],[20],[22],[24],[25],[26],[27],[28],[29],[30] irritation of the bone by the tumor without bony invasion, [16],[17],[18] stimulation of osteoblasts in normal bone by factors secreted by tumor cells, [5],[6],[8],[9] production of bone by the tumor itself [11],[12],[13],[14],[15] and vascular disturbances caused by the tumor. [2],[11],[12],[13],[14],[15] In 1934, Echlin suggested a direct association between hyperostosis and tumor invasion of the bone. [5] Since then, tumor invasion as a cause of hyperostosis has been gaining ground. [2],[3],[4],[5],[6],[7],[8],[9],[10],[19] This study shows the presence of tumor cells in the bone overlying a meningioma in 20% of the cases. In cases showing hyperostosis, the tumor cells were present in 23.3%. These results indicate that tumor invasion into the bone is present in a significant number of patients with meningioma, especially those showing hyperostosis. While the fact that tumor cells are seen in the overlying bone has been established by this study, it remains to be elucidated whether tumor invasion is the cause or the result of bony changes. The former scenario seems less likely as a number of meningiomas not showing tumor invasion of the bone had hyperostosis on radiology (23 out of 32 cases not showing tumor invasion as shown in [Table 1]), thus negating the possibility that the invading tumor cells are responsible for the increased bone production. Also, the occasional occurrence of tumor invasion without hyperostosis (one out of ten) rules out the possibility of tumor invasion occurring as a result of hyperostosis. It is more likely that reactionary changes in the bone due to the close proximity to the tumor and their shared blood supply lead to production of growth factors which stimulate bone production, leading to hyperostotic changes with attendant release of chemotactic factors that attract the tumor cells into the bone matrix. We hypothesize that there may be a common pathogenetic pathway, yet to be explained, which leads to both the bony changes and tumor invasion into the bone.

In his landmark study published in 1957, Simpson elaborately described the importance of the degree of resection in preventing recurrence in meningiomas. He noted recurrence rates of 9, 19, 29 and 40% in Simpson Grade I through IV respectively. [31] Although the series was reported prior to the advent of CT, MRI and microneurosurgery, a number of subsequent studies on the rate of recurrence in meningioma have upheld the principle that clinical success in meningioma surgery is related to the extent of resection. [19],[32],[33],[34],[35],[36],[37],[38],[39],[40],[41],[42],[43],[44] Therefore, in order to achieve complete excision and ensure lower recurrence rate, one should also remove the bone infiltrated by the tumor. However, it is not possible to predict which patients are likely to show bone invasion on the basis of either preoperative radiology or intra-operative pathological evaluation as invasion can occur without hyperostosis on radiology and frozen section examination of bone is not feasible. Therefore, in order to achieve higher Simpson grade of tumor excision, one should remove as much bone in contact with the tumor as possible whenever feasible. In skull base meningiomas, this can be achieved by drilling the bone, especially the hyperostotic areas. In cases of convexity meningioma, which showed the highest rate of tumor invasion into the bone (33% in our study), one should not replace the bone flap and instead use an artificial bone flap to cover the defect.


 » Conclusions Top


Our study shows that a significant number of patients with radiological hyperostosis have tumor invasion into the bone. However, the absence of hyperostosis does not mean the absence of tumor invasion. The authors recommend that one should remove the bone (flap) whenever possible in order to achieve total excision of the tumor and use synthetic material to cover the defect.

 
 » References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2]

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