Histopathology of post-embolized meningiomas

Although embolization of meningiomas has been performed for many years as a preoperative adjunct to reduce tumor vascularity and facilitate surgical excision, little has been written about the features of the histological artefacts introduced by the process. In particular, the fact that it may produce tumor necrosis may potentially cause confusion with atypical or malignant meningiomas. In this study, 25 meningeal tumors of different histological subtypes, all of which had been previously embolized, were reviewed histologically as well as with immunostaining for the MIBI antigen and proliferating cell nuclear antigen (PCNA). Necrosis, in the form of confluent necrosis as well as micronecrosis, was the most common feature (48%). Other characteristic features included florid ischemic changes (16%), intravascular Ivalon particles (24%), and fibrinoid necrosis of vascular walls (12%). Histological changes showed no obvious relationship with the interval between embolization and surgery. There was an increase in MIB1 and PCNA labelling indices in those tumor exhibiting necrotic foci, but it did not seem to have any prognostic significance. We believe pathologists should be familiar with the histological changes induced by embolization in meningiomas so that an erroneous diagnosis of a high-grade lesion will not be made.