cne21th

2007 WHO Grading Scheme for Meningiomas*
WHO grade	Histological Subtype	Histological Features
I	meningothelial, fibroblastic, transitional, angiomatous, microcystic, secretory, lymphoplasmacytic metaplastic, psammomatous	does not fulfill criteria for Grade II or III
II (atypical)	chordoid, clear cell	4 or more mitotic cells per 10 hpf and/or 3 or more of the following: increased cellularity, small cells, necrosis, prominent nucleoli, sheeting, &/or brain invasion in an otherwise Grade I tumor
III (anaplastic)	papillary, rhabdoid	20 or more mitoses per 10 hpf and/or obviously malignant cytological characteristics such that tumor cell resembles carcinoma, sarcoma, or melanoma

*From Perry A, et al : Meningiomas, in Louis DN, Ohgaki H, Wiestler OD, Cavenee
WK, Burger PC, Jouvet A, et al. (eds): World Health Organization Classification
of Tumours of the Central Nervous System, ed 4. Lyon: IARC, 2007, pp 164–172.