Neoplastic Lesions of the CNS

Neoplastic Lesions of the CNS
Meningiomas
are predominantly benign tumors of adults, usually attached to the dura, and arising from the meningothelial cell of the arachnoid.
Meningiomas may be found along any of the external surfaces of the brain as well as within the ventricular system, where they arise from the stromal arachnoid cells of the choroid plexus.
They usually come to attention because of vague nonlocalizing symptoms, or with focal findings referable to compression of underlying brain.

Morphology
Macroscopically:
Meningiomas grow as well-defined dural-based masses that compress underlying brain but are easily separated from it, round ,firm , lobulated mass ,as seen in picture (1,2) .
Microscopically:
There are many different histologic patterns found in meningiomas, including:

syncytial, named for the whorled clusters of cells that sit in tight groups without visible cell membranes;

fibroblastic, with elongated cells and abundant collagen deposition between them; as seen in picture (3,4 ) .

Astrocytoma
Malignant tumors of neuroglial cells . They are most frequent in the fourth through sixth decades.
They are usually found in the cerebral hemispheres.
The most common presenting signs and symptoms are seizures, headaches, and focal neurologic deficits related to the anatomic site of involvement.

Astrocytomas show a spectrum of histologic differentiation that correlates well with clinical course and outcome.
Based on the degree of differentiation, they are classified into three groups: Fibrillary astrocytoma, anaplastic astrocytoma, and glioblastoma multiforme, the least differentiated of all.

Well-differentiated fibrillary astrocytomas
are characterized by a mild to moderate increase in the number of glial cell nuclei, somewhat variable nuclear pleomorphism, and an intervening feltwork of fine, GFAP-positive astrocytic cell processes that give the background a fibrillary appearance, as seen in picture (5 ).

Glioblastoma multiforme (GBM)
show regions that are more densely cellular and have greater nuclear pleomorphism; increased mitoses are often observed,
necrosis and vascular or endothelial cell proliferation surrounded by a rim of dense cells crowded forming palisaded shape so called pseudo-palisading necrosis. as seen in picture (6,7)