En Plaque Meningiom

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En plaque meningiomas refer to a specific meningioma macroscopic appearance characterized by diffuse and extensive dural involvement, usually with extracranial extension into calvarium, orbit, and soft tissues. These tumors are thought to have a collar-like or sheet-like growth along the dura mater, different from the usual globular meningiomas.

See the article on meningiomas for a broad discussion on this entity.

Terminology

There is no absolute and fool-proof way of defining an en plaque meningioma from a flattish globular meningioma with an extensive dural tail (although it is important to note that the dural tail does not actually contain tumor cells). Furthermore, as en plaque meningiomas often have dramatic osseous involvement these tumors are often (erroneously) termed intraosseous meningiomas, a term which should probably be reserved for primary intraosseous meningiomas (i.e. those without intracranial extension).

Pathology

Although locally invasive, this tumor presentation usually corresponds to a WHO grade I meningioma. Meningothelial cells are known to invade and expand the calvarial bones promoting local bone thickening. The extensive hyperostosis, which is frequently seen, is associated with infiltration of the medullary spaces by whorls and syncytia of meningothelial cells .

Radiographic features

Both CT and MR imaging are useful to evaluate the extent of extradural and calvarial involvement. These tumors commonly occur in the sphenoidal ridge, calvarium or spinal region.

Treatment and prognosis

Due to the extensive and invasive presentation of these tumors, sometimes closer to vital structures, complete resection is usually not achievable.Partial removal can lead to a higher chance of recurrence .