Cystic tumors and large size of pediatric meningiomas at presentations are significant macroscopic features reported [2, 15, 25, 27]. Histopathologically there seems to be higher representation of atypical and malignant (WHO grades II and III) associate with these features.

Meningiomas are currently divided into 13 histological types, separated over 3 grades according to the WHO grading system. Majority of these tumors are grade 1 and considered benign (meningothelial, psammomatous, transitional, fibrous, etc.). The atypical (grade 2) tumors are chordoid, clear cell, and atypical; and grade 3 (anaplastic) tumors are rhabdoid, anaplastic, and papillary [32]. These have been associated with prognostic significance.

Immunohistochemistry in recent years has been of significant importance in diagnosing these tumors. MIB-1 is an anti-Ki67 monoclonal antibody which is immunoreactive for the nuclei of cells in non-G0 phases [13]. The ratio of MIB-1-positive cells (MIB-1 index) is reported to correlate well with histological grading. High immunohistochemical proliferation index is found to be associated with increased risk of recurrence [33]. Sandburg et al. [33] studied 14 pediatric tumors and found MIB-1 index of 12.3 % (range 7–31.6 %) in atypical and malignant and 7 % (range 1.2–12.6 %) for grade I meningiomas. When patients with NF2 or history of radiation were excluded, the difference between the MIB-1 index medians for benign and atypical/malignant tumors was even more significant (median of 8.4 % vs. 25.7 %). The authors concluded that the elevated MIB-1 index correlated well with atypia and more aggressive behavior of pediatric meningiomas. Im et al. [25] observed high MIB-1 (≥5 %) in 3 of 11 cases and noted recurrence after 2 years in one case with transitional meningioma and MIB-1 of 10 %. They also noted direct correlation of higher MIB-1 and size of the tumor (5–9 cm), while all were grade one tumors with different histological subtypes. Also Perry et al. [34] studied 19 sporadically occurring pediatric and 14 children and 7 adults NF 2 associated meningiomas in details. The percentages of high-grade (II and III) tumors were 57 %, 60 %, and 67 % in pediatric non-NF2, pediatric NF2, and adults with NF2, respectively. The rate of recurrences was highest in the pediatric non-NF2 patients of 50 % vs. 23 % in pediatric NF2 tumors and 40 % in adults with NF2.

The number of mitotic figures per high power field (1 HPF = 0.16 mm²) is one of the WHO criteria for grading of meningiomas. According to these criteria, 4 or more mitosis/10 HPFs is consistent with atypical meningiomas, and 20 or more is consistent with anaplastic types. The identification of the morphological changes within cells and consequently accurate diagnosis can be difficult. Recently a mitosis-specific antibody against phosphorylated histone H3 (PHH3) has been developed which makes identification of proliferating cells much more accurate [13].

Meningiomas in particular fibroblastic type may be difficult to differentiate from schwannomas with routine staining, especially when located in posterior fossa or spinal canal. Commonly, immunostaining for epithelial membrane antigen (EMA) is significantly higher in meningioma and S100 in schwannoma, but neither immunostain is 100 % specific. For this purpose, another immunohistochemical stain for claudin-1, a key structural protein of tight junctions, has been developed that reacts with meningioma cells but has been shown to have no reactivity with schwannomas [14].

In more recent studies, the incidence of atypical pediatric meningiomas is reported between 11 and 18 %, while grade III meningiomas were around 7 % [4, 5, 8].

Before considering the approaches to the pediatric meningiomas, it is important to point out that the concept of outcome in pediatric neurosurgery patient is perhaps more complex and multifaceted. The factor that plays a significant role in this long-term outlook is the child’s development both cognitively and socially, in order to allow the child to become at least independent or ideally a functional member of the society. The care for the pediatric patient becomes even more complex as one is faced with the child’s carers (usually very anxious parents).

Observation in pediatric posterior fossa meningiomas may be justified for short term but suboptimal for long-term management of these tumors [1]. In the short term, observation may be appropriate to optimize the patient conditions or in cases of small tumors when there is little or no neurological deficit or significant mass effect. However, although these tumors are slow growing, the long-life expectancy of children and the presence of mass effect during their developmental period necessitate definitive management in the long term.

Surgery has been the main stay of treatment of pediatric posterior fossa meningiomas and is found to be the main factor affecting the long-term outcome in this population [4, 5, 34]. Factors complicating surgery include unusual location in the posterior fossa, large size, compression of the lower cranial nerves, infiltration and obstruction of the sinuses, and tumor vascularity, as well as patient-related factors due to prolonged surgery and risks of hypothermia and massive blood transfusion [26].

Recurrence is reported in many series mostly in association with subtotal resection. Given that these lesions are mostly benign and been shown to have good prognosis with total resection, complete surgical resection should be attempted while avoiding further neurological deficit.

With the importance of complete resection being increasingly realized, it has been suggested the complete resection should be attempted even if this is done in two or three stages [35]. Some authors also suggest “second-look” surgery in order to avoid radiation and its long-term complication including secondary tumors [27, 36]. Staged surgery is also an option for the cases with high blood loss [27]. In our institution we take the approach of maximal resection even if this may require further surgery, in order to avoid radiation and its long-term complications [1].

Risk factors for perioperative mortality include tumor characteristics such as the size, location within the posterior fossa, and the vascularity of the tumor. In a series of 152 combined cases, 5 perioperative deaths were recorded [27]. Three died due to brainstem injury and intraoperative hemorrhage, respectively, and two died of intracranial infection. On their review of literature, Liu et al. reported perioperative mortality between 0 and 8.3 % with the mean mortality of 3.3 % [27].

Significant brain edema as cause of perioperative death has been reported in several series [26]. Arivazhagan et al. [26] suggested preoperative CSF diversion, anti-edema measures, and postoperative ventilation as some of strategies to avoid this complication.

The utility of radiation in the treatment of meningioma has been demonstrated in adult tumors. Local control and recurrence rates differ between studies, with rates between 46 % 5 years local control and 100 % 10 years recurrence-free probability being reported [20]. However, it is generally recognized that surgical resection continues to offer superior local control than radiation, for cases where it is suitable. The role of radiation therapy as an adjunct to surgery, in cases of incomplete resection, is more universally supported, particularly in cases of WHO grade 2 and 3 tumors [20].

Before considering radiation in children, however, potential adverse effect such as secondary tumors, hormonal deficiency, growth retardation, or cognitive impairment, particularly in younger patient, must be weighed again potential benefits [1].

Libel and colleagues used upfront radiation to delay recurrent tumor [32]. However, some others have suggested re-operation as an option for avoiding radiation for recurrent tumors [26]. The reason for postoperative radiotherapy has been mostly with recurrent tumor or presence of atypical or malignant tumors in most series [5, 8, 9, 20]. In series reviewed, radiotherapy was recommended for high-grade tumors in children older than 5 years of age and in particular where residual was present and further surgery was not feasible.