Cytological changes induced by embolization in meningiomas

To describe cytological changes in meningiomas induced by embolization, which may be carried out a few days before surgery in order to soften the tumour and minimize intraoperative bleeding. Although histological changes have been described, we have found no description of such changes in the cytological literature.

We reviewed 22 cases of meningiomas with prior embolization in which cytological material was obtained during intraoperative consultation. In 13 of them recognizable cytological changes induced by embolization were present. On histology, these 13 tumours were grade I and showed intravascular embolic material.

Cellular dissociation was prominent, with frequent single cells and small groups. Ischaemic cellular changes were a common finding and consisted of cell shrinkage, nuclear pyknosis and karyorrhexis. Confluent areas of necrosis were seen in one case. Additionally, numerous macrophages were present, many containing cellular debris, and neutrophils, giving a characteristic appearance of acute cellular ischaemia. Embolic material was seen cytologically in four cases as well-defined spherules surrounded by empty halos. Features of viable meningioma were recognized in all cases.

Embolization of meningiomas induces cytological changes that mirror those seen on histology, but cellular dissociation with changes of ischaemia may result in a worrisome image. When faced with such changes the pathologist should consider the possibility of embolization, avoiding misdiagnosis of higher grade meningioma or metastatic carcinoma.