Atypical and ischemic features of embolized meningiomas

Preoperative embolization (POE) of meningiomas is widely used to facilitate surgical removal and to reduce intraoperative blood loss. The resulting necrosis and enhanced proliferation have been reported to affect subsequent histologic grading. However, there was little concern about ischemic features, for example small cells resembling atypical meningiomas, cytoplasmic vacuoles resembling clear cell meningioma, intercellular discohesion resembling rhabdoid meningioma, and perivascular cuffs resembling papillary meningioma. Therefore, the extent of these ischemic features was scored and Ki-67 staining indices were investigated in a POE group composed of 29 specimens of meningiomas treated with POE and compared with equivalent results for a non-POE group composed of 29 meningiomas that were not treated with POE. Small cells with high N/C ratios, cytoplasmic vacuoles, intercellular discohesion, and perivascular cuffs were significantly increased in the POE group (versus the non-POE group, p < 0.05). There were no significant differences of the Ki-67 index between the POE group (2.2%) and the non-POE group (1.9%) (p = 0.49). Our results suggest that small cell change resulting in necrosis may be followed by POE, and that clear cell-like, rhabdoid cell-like, or pseudopapillary pattern identified in meningiomas may also be induced by POE. Therefore, histological findings and determination of grading should be evaluated cautiously in cases of embolized meningiomas.