Ectopic Meningiomas

Abstract

Four cases are reported of ectopic meningioma of the frontal sinus, maxillary antrum, orbital fossa, and scalp. The tumors contain cellular whorls and psammoma bodies, the diagnostic hallmarks of meningioma. The concept of cellular origin of meningioma is reviewed and it is concluded that meningocytes, fibroblasts, and Schwann cells are mesenchymal type cells. We suggest that meningioma arises directly from any one, or a combination, of these cells as well as from mesenchymal cells. This concept explains the diverse histological features of meningioma as being associated with multipotentiality of mesenchymal type cells. In addition, this concept clarifies why meningioma is easily confused microscopically with the nerve sheath tumors, because they are all mesenchymal neoplasms. © 1973, American Medical Association. All rights reserved.