In 1990 Al-Rodhan and Laws published a historical account of meningiomas and its surgical management.1 The interest in meningiomas has not declined since then. In 1922 Cushing2 wrote “There is today nothing in the whole realm of surgery more gratifying than the successful removal of meningioma with subsequent recovery.” These words stand true more than 80 years later. Meningiomas are the most common primary non glial tumours and comprise 13-19% of all primary intracranial tumours.3 The WHO developed a new comprehensive classification of central nervous system neoplasms, where meningiomas are regarded as a heterogeneous group of mesenchymal tumours with three grades.4 The characteristic morphology of the benign and malignant tumours has been exhaustively described earlier. The existence of an intermediate group of meningiomas, exhibiting less favourable biological behaviour than classic benign tumours but a relatively more favourable biological behavior than malignant tumours has been described. They have been referred to as atypical meningiomas.

In this retrospective study, 468 operated cases of meningiomas at the Bombay Hospital Institute of Medical Sciences, Mumbai,(January 2000 to November 2004) were analyzed. Histological sub typing of these tumours was done as per the W.H.O. classification.4 The clinical data, neuroradiological investigations like magnetic resonance imaging (M.R.I.) , computed tomography (C.T. Scan) and type of treatment were studied in detail. The slides were stained with routine haematoxylin and eosin stains. The recent W.H.O. classification for diagnosing atypical and anaplastic (malignant) meningiomas appeared to be the most appropriate and we adopted the following grading criteria, which included (a)increased mitotic activity > 5 mitosis per 10 H.P.F (b) increased cellularity (c) small cells with high nucleo - cytoplasmic ratio (d) sheeting of tumour cells with loss of typical histological pattern (e) prominent nucleoli (f) foci of spontaneous or geographic necrosis and (g) absence of tumour invasion into cortex in atypical meningiomas.

World Health Organization (Who)
Classification for Meningiomas

Out of the 468 cases operated at this institute, 21(4.48%) were classified as atypical meningiomas, 8 (1.7%) as malignant and the remaining as benign. Tables 1 and 2 highlights the clinical features of atypical meningiomas including age, sex, site of the tumours, treatment and history of recurrences. Figs. 1 and 2 show the histologic features of atypical meningiomas.

Out of the 21 patients, 19 were males and 2 females (M/F 9/1). The youngest patient at the time of first surgery was 15 years and the oldest 74 years (mean 52 years, median 55 years). Signs and symptoms were present for 4 weeks to 2 years before diagnosis. Symptoms of raised I.C.T such as headaches, vomiting, seizures and focal neurological deficits were present.

Fig. 1 : H and E Stain showing nuclear pleomorphism (x 40).

The parasagittal and parafalcine regions represented the most common site of tumour (47.6%) followed by the convexities (33%), posterior fossa (9.5%) and the olfactory region (9.5%). Thirteen patients underwent total resection (Simpson Grade I extirpation). The remaining 8 patients were subjected to subtotal resection (Simpson Grade II extirpation), due to inaccessibility or huge size of the tumours. One patient who had total resection of the tumour expired in the immediate postoperative phase. Radiotherapy was given to 3 patients with total resection and 1 with subtotal resection. A postoperative follow up study revealed that 11 patients (52.3%) suffered recurrences of which 5 had total resection of the tumour and 6 subtotal resection. The recurrences occurred 1 to 21 years after surgery. The mean time of first recurrence was after 7.9 years whereas the median time to the first recurrence was 5 years. The number of recurrences per person varied from two to five, with a mean of 3. Grossly the tumours were well defined, grey brown and ranged from 2.5 cms to 8 cms. Transtitional meningioma constituted the most common type of tumour (18 cases). The other types included meningothelial meningioma (1 case) and angioblastic meningioma (2 cases). In addition to high cellularity and varied degree of pleomorphism, all cases had > 5 mitosis / 10 H.P.F. One case had papillary pattern. None of the tumours showed microscopic cerebral invasion.

Fig.2 : H and E Stain showing mitoses and high cellularity.

Skullerud et al5 regarded high cellularity as one of the indicators of recurrence of atypical meningiomas. Jellinger et al6 stated high cellularity and increased mitotic index might account for recurrence. Necrosis7 has also been regarded as an indicator of recurrence. The recent W.H.O. classification provides a broader criteria to differentiate atypical and malignant meningiomas. In the present study twenty one cases that fulfilled the W.H.O. criteria were diagnosed as atypical meningiomas and formed the base of this study. There were 19 males and 2 females with an average age of 52 years. This is comparable with previous reports which state that the male gender was predominant (Thomas et al,8 Sano et al9. Postoperative follow up showed 11 patients had recurrence (52.3%) ( W.Y.K. Chen et al10). Median time to the first recurrence was 5 years and the number of recurrence per person varied from two to five, with a mean of 3 which was similar to findings reported by Lucio Palma et al.11 In our study all the cases of atypical meningiomas showed > 5 mitosis 10 H.P.F., but the number of mitotic figures per se did not affect the recurrence. We thus share the same observations with Jellinger et al6 that mitotic rate alone appears to be of no prognostic value. The recurrence rate also did not relate to any histological subtype (W.Y.K. Chen et al.10 )

The completeness of the surgery is the single most important prognostic factor as brought out by our study. This is also substantiated by other workers. (Kinjo et al,12 Borovich et al13). The prognostic influence of radical surgery in our study is emphasized by the fact that out of the 7 meningiomas of the convexities 6 had Simpson Grade I extirpation and 1 Simpson Grade II. The tumours that were totally resected did not show any recurrence except one. The one that did recur was after 23 years of surgery.11 The tumour which had Simpson Grade II extirpation recurred just after two years of surgery ( Lucio Palma et al11). Out of the 10 tumours of the parasagittal, parafalcine and tentorial regions 4 patients had total resection and 6 subtotal resection. 8 of these recurred out of which 5 were resected sub totally. The other 3 recurred even after supposedly Simpson Grade I extirpation was carried out. This can be explained by the fact that true Simpson Grade I extirpation can only be accomplished for tumours located in the cerebral convexities, and not in the parasagittal / parafalcine regions.12,13 Even though both the tumours situated in the olfactory region were treated by total resection, 1 recurred due to its large size and involvement of the surrounding anatomical structures. 1 out of the 2 patients having posterior fossa lesions underwent total resection and succumbed immediately due to its proximity to vital structures of the brain. The other who had subtotal resection did not have any recurrence. Thus it can be concluded that out of the 13 tumours that were resected totally 5 showed recurrence. These recurrences could be explained by the fact that 3 were tumours of the parafalcine/ parasagittal regions, 1 of the orbit12,13 and 1 of the frontal lobe which recurred only after 23 years of surgery.

Postoperative radiation therapy was used in 3 patients, who supposedly had total resection of the tumours. But the tumours recurred in 2 patients because one had tumour involving the orbit and the surrounding anatomical structures and the other, the parafalcine region.14 Radiation therapy used in 1 patient who had subtotal resection for a tentorial based meningioma showed postradiation recurrence due to incomplete removal of the tumour