Ossified Intracranial Meningiomas: Description of the First Series of Cases and Review of the Literature

Abstract

Metaplastic meningiomas are characterized by mesenchymal differentiation with formation of bone, cartilage, fat, or xanthomatous elements. However the presence of extensive areas of ossification is rare in meningiomas. In addition, intracranial location of ossified meningiomas is uncommon. Surgical management represents the optimal treatment for ossified meningiomas, but ossification may interfere with surgery and condition outcome. By reviewing patient records and contacting patients, families, and referring physicians, the following information was gathered: age, sex, tumor location, clinical presentation, preoperative and postoperative functional status, and surgical data. Each surgical specimen had been formalin-fixed, paraffin-embedded, and cut into parallel 4-μm-thick sections for histological evaluation. Our literature search identified 8 cases, all of whom had undergone surgical treatment. Histopathological analysis revealed the presence of disorganized bone spicules with solitary oval osteocytic nuclei and lined by osteoblasts, with clear evidence of bone tissue in at least 50% of tumor tissue. Here we present the largest series, to our knowledge, of surgically treated intracranial ossified meningiomas reported to date. The mechanism of ossification in these meningiomas remains unclear, and various hypotheses have been formulated. Complete lesion removal, or subtotal debulking in those cases characterized by tenacious adherences to vascular structures and/or critical areas, may represent the optimal treatment.