- Aggressive tumor in children: There are many subtypes of meningioma, and all of them are seen in children. Although not uniform in the literature, there tends to be a predilection towards more malignant subtypes in children (3). Pathological grading and extent of resection appear to have the greatest impact on disease-free progression and survival.
- EMA: Common in meningotheliomatous type (7).
- MIB-1: Correlates with tumor grade (7).
- Progesterone receptor (PR): Found in children even though tumors are not apparently hormonally driven (4).
Given the rarity of this tumor in children, it is not possible to collect sufficiently large numbers of cases to establish reliable clinical outcome measures on the basis of grading criteria.
- W.H.O. I: Typical meningioma. These are the histological variants other than clear-cell, choroid, papillary or rhabdoid. They lack the criteria of an atypical or anaplastic meningioma as stated below.
- W.H.O. II: Atypical meningioma. These have a high mitotic index (>4/HPF) and at least three of the following characteristics: sheeting architecture, macronucleoli, small cell formation, hypercellularity, necrosis, and/or direct brain invasion.
- W.H.O. III: Anaplastic/malignant. These exhibit frank anaplasia and have a very high mitotic index (>10/HPF).
- Fibroblastic: The fibroblastic variant is characterized by fascicular growth of fibroblast-like spindle cells.
- Meningothelial: The meningothelial variant is characterized by syncitial growth of meningothelial cells.
- Angiomatous: The angiomatous variant is characterized by numerous densely packed blood vessels.
- Psammomatous: The psammomatous variant is characterized by presence of numerous clacified psammoma bodies.
Aggressive subtypes occurring in children (all W.H.O. II)
- Clear cell: The clear cell subtype is characterized by clear glycogen-rich cytoplasm.
- Choroid: The choroid subtype is characterized by chordoma-like growth of tumor cells in a myxoid matrix.
- Papillary: The papillary subtype is characterized by pseudopapillary growth pattern.
- Rhabdoid: The rhabdoid subtype is characterized by large rounded tumor cells with eccentric nuclei.