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Year : 2000  |  Volume : 48  |  Issue : 4  |  Page : 338-42

Atypical meningioma : a clinicopathological analysis.

Departments of Pathology and Neurosurgery, Sree Chitra Thirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, 695011, India.

Correspondence Address:
Departments of Pathology and Neurosurgery, Sree Chitra Thirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, 695011, India.

  »  Abstract

In this retrospective study, 382 operated cases of meningiomas were reviewed. 32 cases (8.3%) were histopathologically classified as atypical meningioma. The anatomical locations and histological features in all the thirty-two cases were correlated with their recurrence rates and biological behaviour. The overall recurrence rate for atypical meningioma within two years was 28% as compared to 9.3% in benign meningiomas. It is being emphasized that an accurate histopathological interpretation of atypical meningioma is essential for predicting the recurrence, biological behavior as well as post-operative management modalities.

How to cite this article:
Joseph E, Sandhyamani S, Rao M B, Nair S, Radhakrishnan V V. Atypical meningioma : a clinicopathological analysis. Neurol India 2000;48:338

How to cite this URL:
Joseph E, Sandhyamani S, Rao M B, Nair S, Radhakrishnan V V. Atypical meningioma : a clinicopathological analysis. Neurol India [serial online] 2000 [cited 2023 Feb 4];48:338. Available from: https://www.neurologyindia.com/text.asp?2000/48/4/338/1504

   »   Introduction Top

Meningiomas are the most common primary non-glial intracranial brain tumours and comprise 13-19% of all primary intracranial neoplasms.[1] Meningiomas are usually benign and arise from arachnoidal cells. In the recent WHO classification, meningiomas are regarded as a heterogeneous group of tumours and are histologically categorized into 14 distinct subgroups with three grades of malignancy.[2] The characteristic morphology of these usually benign tumours and of malignant variants has been exhaustively described earlier. The existence of an intermediate group of meningiomas, exhibiting less favourable biological behavior than classic benign tumours but a relatively more favourable biological behavior than definitive malignant meningiomas, has been described in the recent WHO classification of central nervous system tumours.[2] They have been referred to as atypical meningioma. In this study, we applied the criteria described by Mahmood et al[3] in analysing 32 cases of atypical meningioma. There are no published reports from the Indian subcontinent, highlighting atypical meningiomas.

   »   Materials and methods Top

In this retrospective study, 382 operated cases of meningiomas at the Sree Chitra Thirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, from January 1990 to December 1995, were analysed. Histological subtyping of these tumours were done as per the WHO classification.[2] All the slides reported earlier as atypical meningioma were reviewed. The histological features of atypical meningiomas are depicted in [Figure. 1] and [Figure. 2]. Wherever required, additional paraffin sections were studied. Apart from routine haematoxylin and eosin stain, reticulin and Masson's trichrome stains were done. Grading of the atypical meningioma was applied on the basis of definite histopathological parameters[3] [Table I]. Partial scores were added to obtain cumulative scores. Tumours with total scores ranging from 0 to 4 were regarded as benign, 5 to 11 as atypical and > 11 were regarded as malignant meningioma. The clinical features and post-operative follow up data in these cases were reviewed in detail.

   »   Results Top

Out of the 382 cases of meningiomas operated at this Institute, 349 (91.4%) were classified as benign, 32 (8.3%) as atypical and 1 (0.3%) as malignant meningiomas. [Table II] highlights the clinical features, histopathological score and post-operative follow-up data of atypical meningioma. The peak incidence of atypical meningioma occurred in the fourth decade, whereas benign meningiomas showed a peak incidence in the fifth decade. There is no difference in the sex distribution between atypical meningioma and benign meningioma. The most common anatomical location of atypical meningioma was the parasagittal region (43.7%), followed by the cerebral convexities (15.6%). Neuroradiological investigations like computed tomography (CT) and magnetic resonance imaging (MRI) were available in all cases. Neuroradiological features were regarded as meningioma with peritumoural oedema. Out of the 32 cases, 21 had undergone total excision while 11 had only subtotal excision. One patient expired in the immediate post-operative phase due to hypothalamic dysfunction. Radiotherapy was given to 11 cases in whom the surgical excision was subtotal. Extracranial metastasis was not recorded in any patient. In 14 out of 32 cases of atypical meningioma, the histological scoring was between 8-11 and in 18 between 5-7. All the patients, except 4, were regularly attending the post-operative neurosurgical clinic for a period ranging between 9 months to 7 years.
The postoperative follow-up data of 32 cases of atypical meningioma was reviewed from the case records. Twelve cases manifested recurrence (37.5%). In five out of 12 recurrent cases, the surgical excision was total. The scoring in all the 5 cases was above 8. In 10 out of 12 recurrent cases, the histological scoring in the initial specimen ranged between 8-11 and in 2 cases the scoring was between 5-7. The mean time of recurrence in atypical meningioma with scores between 8-11 was 19.8 months while in those with scores between 5-11, the mean was 35 months. Therefore recurrence rate was statistically significant in atypical meningioma with high scores (p<0.05). At 2 year follow-up, 9 cases of atypical meningioma (28%) and 3 cases of benign meningioma recurred (9.3%). Among 349 benign meningiomas, 14 cases recurred in 7 years. There was no difference in the histopathological features, both in the first and recurrent specimens, in the benign variants. However in 3 atypical meningiomas, the scores became 9 in the recurrent specimen, from the initial score of 7.

   »   Discussion Top

Meningiomas have been recognized as a tumour entity for nearly 200 years.[4] They are usually considered as benign. Jaaskelainen et al[5] and later Rohringer et al[6] attempted to classify these tumours by using a numerical grading system. Their grading criteria, however, were not elucidated completely and thus remained only subjective. Secondly, this could not be applied on a prospective manner. The recent WHO classification provides a broad criteria for differentiating benign and atypical meningioma. Skullerud et al[7] regarded high cellularity as one of the indicators of recurrence of these tumours. Jellinger et al[8] felt high cellularity and increased mitotic index might account for recurrence. Necrosis,[9] mitotic Figures and focal necrosis[10] has been regarded as indicators of recurrence. Numbers of macrophages and T and CD8 lymphocytes in meningiomas have been related to atypical histology.[11] The grading system proposed by Mahmood et al[3] appears to be the most appropriate one and these criteria include increase in mitotic rate, high cellularity, sheeting of tumour cells with loss of typical histological pattern, prominent nucleoli, focal necrosis, tumour invasion into cortex or bone. We have adopted the above grading criteria.
In the present study, the atypical meningioma occurred a decade earlier as compared to benign meningioma. The recurrence rate of atypical meningioma, within two years, was 28% as compared to 9.3% for benign meningioma. Jaaskelainen et al[5] reported recurrence rate of 38%. Recent studies have shown that the recurrence of meningiomas appears to be modulated by their proliferative potentials. Bromodeoxyuridine labelling index, proliferative cell nuclear antigen (PCNA),[12] argyrophilic nucleolar organizer region (AgNOR) count[13] and Ki-67 staining index[14] have been used to assess the proliferative potentials in atypical meningioma. Evaluation of Ki67 immunohisto-chemical activity within the neoplastic cells can identify recurrence prone meningioma.[15] Niedermayer et al[16] concluded that Ki-67 indices and cytogenetic features support a clearer definition of the intermediate meningioma.
The histopathological criteria for the accurate interpretation of atypical meningioma have been well defined in this study. This scoring system clearly distinguished benign atypical variant of meningioma. It is being emphasized that the surgical pathologists should be familiar with these criteria and the scoring system should be kept at the reference desk at the time of reporting. An accurate interpretation of the atypical meningioma is essential since these tumours are likely to recur much earlier than benign variants. Although all meningiomas having score between 5-11 were grouped as atypical meningioma, the results of this study suggest that post-operative radiotherapy is warranted in patients with atypical meningioma having scores between 8-11. This will decrease recurrence rate as well as the neurological deficits and complications in patients with atypical meningioma.


  »   References Top

1.Kepes JJ : Meningiomas. Biology, pathology and differential diagnosis. Masson, New York. 1982.   Back to cited text no. 1    
2.Kleihues P, Burger PC, Scheithauer BW : Histological typing of tumors of the central nervous system: World Health Organization, Ed 2: Springer, Berlin. 1993.   Back to cited text no. 2    
3.Mahmood A, Caccamo DV, Tomecek FJ et al : Atypical and malignant meningiomas : A clinicopathological review. Neurosurgery 1993; 33 : 955-963.   Back to cited text no. 3    
4.Su CF, Shih CJ, Tsou CK : Malignant meningiomas: Clinical and pathological study of 10 cases: Taiwan I huueh Hui Tsa Chih 1986; 85 : 608-623.   Back to cited text no. 4    
5.Jaaskelainen J, Haltia M, Servo A : Atypical and anaplastic meningioma: Radiology, surgery, radiotherapy and outcome: Surg Neurol 1986; 25 : 233-242.   Back to cited text no. 5    
6.Rohringer M, Sutherland GR, Louw DF et al : Incidence and clinicopathological features of meningioma. J Neurosurg 1989; 71 : 665-672.   Back to cited text no. 6    
7.Skullerud K, Loken AC : The prognosis in meningioma. Acta Neuropathol (Berl) 1974; 29 : 337-344.   Back to cited text no. 7    
8.Jellinger K, Slowik F : Histological subtypes and prognostic problems in meningioma. J Neurol 1975; 208 : 279-298.   Back to cited text no. 8    
9.Christensen D, Laursen H, Klinken L : Prediction of recurrence in meningiomas after surgical treatment. Acta Neuropathol (Berl) 1983; 61 : 130-134.   Back to cited text no. 9    
10.Crompton MR, Gautier Smith PC : The prediction of recurrence in meningiomas. J Neurol Neurosurg Psychiatry 1970; 33 : 80-87.   Back to cited text no. 10    
11.Rossi MI, Cruz Sanchez F, Hughes JT et al : Immunocytochemical study of the cellular immune response in meningiomas. J Clin Pathol1988; 41 : 314-319.   Back to cited text no. 11    
12.Karamitopoulou E, Peretes E, Melachriinou M et al : Proliferating cell nuclear antigen immunoreactivity in human central nervous system neoplasms. Acta Neuropathol1993; 85 : 316-322.   Back to cited text no. 12    
13.Radhakrishnan VV, Radhakrishnan NS, Rout D et al : Nucleolar organiser in meningiomas. Br J Neurosurg 1993; 7 : 377-381.   Back to cited text no. 13    
14.Matsuno A, Fujimaki T, Sasaki T : Clinical and histopathological analysis of proliferative potentials of recurrent and non-recurrent meningiomas. Acta Neuropathol 196; 91 : 504-510.   Back to cited text no. 14    
15.Kolles H, Niedermayer I, Schmitt C et al : Triple approach for diagnosis and grading of meningiomas : histology, morphometry of Ki-67/Feulgen staining and cytogenetics. Acta Neurochir(Wien) 1995; 137 : 174-181.   Back to cited text no. 15    
16.Niedermayer I, Kolles H, zang KD et al : Characterization of intermediate type (WHO 'atypical') meningiomas. Clin Neuropathol 1996; 6 : 330-336.   Back to cited text no. 16    


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