Meningothelioma as the predominant histological subtype of midline skull base and spinal meningioma.

OBJECT This study was undertaken to test a hypothesis that meningiomas of the midline skull base and spine are predominantly of the meningothelial histological subtype. METHODS The cases of 794 consecutive patients who underwent resection for meningioma at the Cleveland Clinic between January 1991 and March 2004 were reviewed retrospectively. The authors analyzed the relationship between the tumors' histological subtypes and sites of origin in the 731 patients from this group who harbored tumors that were determined to be benign histologically (World Health Organization Grade I). Meningothelial meningiomas (MMs) accounted for 63.5% (464/731) of the Grade I tumors. The incidence of MM according to the site of origin was as follows: 84.9% (186/219) in the midline skull base, 58.3% (35/60) in the lateral skull base, 48.5% (183/377) in a non-skull base location, and 80% (60/75) in spinal locations. The incidence of MM in the midline skull base and spinal locations were significantly higher than in non-skull base or lateral skull base locations. CONCLUSIONS Meningiomas of the midline neuraxis are predominantly meningotheliomas. Analysis of the increasingly available data on genetic and topographic characteristics of MMs suggests that they may represent a unique entity, contrary to the prevailing belief that all benign meningiomas are identical tumors.