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Washington University Experience | NEOPLASMS (MENINGIOMA) | Papillary | 8C Meningioma, with papillary features, WHO II (Case 8) Ki67 1.jpg
8C Immunohistochemistry for proliferation marker Ki-67 (MIB-1 antibody) stains a regionally variable proportion of tumor cell nuclei, manually calculated in an area of estimated greatest density to range up to at least 4.6%. ---- Comment: This current case, however, does show predominantly papillary architecture, accompanied by only relatively modest atypical features (hypercellularity, focally sheeted architecture, focal macronuclei, and multi-focal spontaneous necrosis), a relatively low mitotic count (<4/10HPF), and no histological evidence of brain invasion. Also more consistent with routine WHO Grade 1 meningioma, the cytogenetic (FISH) profile of this tumor does not provide independent support for a higher grade diagnosis. Given this unusual circumstance of widespread papillary architecture in the setting of an otherwise atypical meningioma, we favor the diagnosis: Atypical meningioma with papillary features, WHO Grade 2.
