Benign Meningiomas Grade

Meningothelial (Syncytial) Meningioma The tumor cells have a round to oval nucleus with scanty chromatin, homogenous cytoplasm, and poorly defined cellular membrane. Some nuclei appear vacuolated from cytoplasmic invagination (pseudoinclusion). The cells form whorls separated by a fine reticulin network (see Fig. 11.28).

A fibrous meningioma consists of elongated and spindle-shaped cells forming interlacing bundles. Reticu-lin and collagenous fibers are abundant (see Fig. 11.28).

A transitional (mixed) meningioma contains elements of both meningoendothelial and fibrous menin-giomas. Concentric whorls of crescent-shaped and

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figure 1 1.28

Meningiomas, histologic features. A and B. Meningothelial (syncytial) meningioma. Moderately large, oval nuclei are surrounded by round or polygonal cytoplasm with poorly defined borders. The cells typically are arranged in whorls (HE). C. The center of some whorls display a psammona body (HE). D. Fibrous meningioma consists of fibrillated spindle cells arranged in interlacing bundles (HE). E. The tumor cells immunoreact for vimentin (immunostain). F. Bony invasion by meningioma (van Gieson stain).

figure 1 1.28

Meningiomas, histologic features. A and B. Meningothelial (syncytial) meningioma. Moderately large, oval nuclei are surrounded by round or polygonal cytoplasm with poorly defined borders. The cells typically are arranged in whorls (HE). C. The center of some whorls display a psammona body (HE). D. Fibrous meningioma consists of fibrillated spindle cells arranged in interlacing bundles (HE). E. The tumor cells immunoreact for vimentin (immunostain). F. Bony invasion by meningioma (van Gieson stain).

elongated cells are characteristic. The centers of the whorls often contain a psammoma body, which develops from calcium deposits in the degenerating tumor cells or from calcium deposits in the thickened, hyalin-ized walls of blood vessels.

A psammomatous meningioma displays numerous psammoma bodies and fewer neoplastic cells.

An angiomatous meningioma has a rich vascular supply, with thickened hyalinized blood vessels. Hemorrhages within the tumors are uncommon.

Microcystic meningiomas contain small mucinous cystic cavities.

Secretory meningiomas contain eosinophilic amorphous round to oval bodies.

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