Meningioangiomatosis-associated meningioma misdiagnosed as glioma by radiologic and intraoperative histological examinations.

As an extremely rare condition, meningioma may occur together with meningioangiomatosis. We report here a case of meningioangiomatosis-associated meningioma misdiagnosed as glioma by preoperative radiologic and intraoperative histological examinations. A 50-year-old woman presented with a 1-year history of headache and dizziness. Magnetic resonance imaging revealed a round left temporal mass located cortically with hypointensity on T(1)-weighted images and hyperintensity on T(2)-weighted images. In the intraoperative histological examination, a diagnosis of glioma was made based on high cellularity and large tumor cells with nuclear atypia. However, postoperative histological diagnosis of the lesion was meningioangiomatosis-associated meningioma corresponding to World Health Organization (WHO) grade I. A part of the cortical lesion showed the histological features of meningioangiomatosis. Neoplastic cells in the meningioma portion were a transitional variant with immunoreactivity to epithelial membrane antigen and low MIB-1 index, up to 1%. The patient has been followed up for 6 months without adjuvant radiotherapy or chemotherapy. No tumor recurrence was found during this period. Meningioangiomatosis-associated meningioma might be erroneously interpreted as tumor invasion by those who were not familiar with this condition. Therefore, removal of sufficient tissue from different portions of the lesion is essential for the neuropathologist to make a precise diagnosis in the intraoperative histological examination.