Meningioma
The meningioma is the neurosurgeon's "friend" and often his most
enduring challenge. For both the physician and patient, this tumor carries
a true tag of benign. It also carries the possibility of "cure" in approximately
80% of cases. Thus, the long-term outcome for a patient with this tumor
is a direct function of the skill and assiduousness of the surgeon who
removes it.
Elsewhere in the Brain Surgery Information Center's Primer on Brain
Tumor Biology, it was mentioned that "benign" often does not really mean
benign. Be assured that in this case, the tumor really is benign.
As mentioned earlier in the Primer, each type of brain tumor arises
from a specific cell type. The cell of origin for the meningioma is call
the arachnoid cap cell, found on the surface coverings (called meninges)
of the brain in the paccionian granulations. These serve as the one-way
valve system between the water system of the brain and the veins that drain
from the brain to the heart.
Interestingly, these tumors have an embryologic relationship with cells
found in the muscle layer of the utereus. In fact, it is exceedingly difficult
for the pathologist to distinguish the meningioma from the fibroid tumors
of the utereus under the microscope. Also, they share the characteristic
female hormonal receptors (estrogen and progesterone) on their cell surfaces.
This characteristic has lead to the testing of anti-estrogen receptor agents,
such as tamoxifin, as a growth-inhibiting agent in these tumors. Clinical
studies to date have failed to provide siginificantly positive results.
Meningiomas are rarely malignant in their behavior. But when malignant,
meningiomas grow rapidly and are destructive; they are quite difficult
to treat, and recur oftentimes in less than a year after surgical removal.
They are also difficult for the pathologist to diagnose under the microscope.
Probably the only finding that correlates well with the diagnosis is that
of numerous cells seen in division ("mitosis"). The pathologist may occasionally
speak of brain and skull invasion, cells with an abnormal appearance, or
other bizarre findings, however none of these completey fit the diagnosis.
Ultimately, the diagnosis is determined by the activity of the particular
tumor over time.
A cousin to the meningioma is the hemangiopericytoma. The cell of origin
for this tumor is the perivascular pericyte (located around blood vessels).
Although very similar to the benign meninigiomas, these tumors tend to
recur with great rapidity (less than one year) and frequency. Some physicians
classify these tumors with the malignant meningiomas.
You can see an operation here, using BRAINLAB's most sophisticated, computer guided O.R. systems and equipment--a boone to today's neurosurgeon. You will be able to follow the operation from the scanning of the MRIs, through the pre-op computer guidance system, to the operation itself and finally to to the actual removal and display of the meningioma.
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