Astrocytomas are the most common (over 70%) of all primary intracranial
Spinal astrocytomas are discussed
The world health organization
(WHO) currently recognizes multiple astrocytic tumor variants.
They may be classified according to their
cytologic characteristics, viz., fibrillary, protoplasmic or gemistocytic;
or according to their location, viz., cerebral, hypothalamic, cerebellar
or brainstem. The latter classification apart from location is also based
upon considerations, partly, of cell type and partly of growth and
behavior of the tumor.
composition is often heterogenous,
fibrillary astrocytes are by far the most frequently observed.
Astrocytes show a
stellate arrangement of fine fibrillary processes. Their nuclei are oval
with scattered chromatin. Diffuse cerebral astrocytomas are composed of
cells with this appearance, and are predominantly of the fibrillary
type. These tumors may contain microcysts and foci of dystropic
Identifying the presence of
these morphological subtypes, however, appears to
have little value in terms of
A possible exception is the 9% to
19% of astrocytomas composed
predominantly of gemistocytic cells.
cases, gemistocytic cell content in
excess of 60% has been
associated with aggressive neoplastic
behavior and a poorer prognosis.
cells are large, globoid, and packed with a hyaline cytoplasm, and
eccentric nuclei with coarse chromatin and conspicuous nucleoli. They show
fibrillary acidic protein
Protoplasmic variant, the
least common variant (<1% of all astrocytomas),
involves cerebral hemisphere superficially. Histologically homogenous
population of small astrocytes with few delicate processes.
Over the years, the notion that histological characteristics
are useful as predictors of neoplastic aggressiveness
has come to be accepted. As a result, current classification
systems assign distinct tumor grades based on
the presence, absence, and degree of specific observable
These criteria commonly include the
overall degree of tumor cellularity, extent of cellular and nuclear
pleomorphism, frequency of
mitotic activity, and presence
or absence of necrosis and endothelial proliferation.
In the WHO
four tier system, similar weight is
given to the presence of
nuclear atypia, mitoses, endothelial proliferation, and necrosis. In the
absence of these criteria, the grade of 0 is assigned. If any of the
criteria can be identified,
a grade of 1 is aligned. Successive grades up to 4 are assigned upon
subsequent identification of any of the remaining criteria. Using this
system, the proportionate distribution of all astrocytomas has been found
to be 4.1% grade 1, 23% grade 2, 16% grade 3, and 57% grade 4.
We follow Daumas-
Duport (St. Anne/Mayo,1988) system. This scheme is restricted to
astrocytomas and glioblastomas. The following histological abnormalities
are used to place tumors in 4 grades: nuclear atypia, mitosis, endothelial
and necrosis. The system
is very reproducible and the grade is strongly correlated with survival.
(nuclear atypia and no/or rare mitosis)
1 (no criteria fulfilled)
2 (one criterion: usually nuclear
atypia and marked mitosis)
criteria: usually nuclear atypia and mitosis)
IV (nuclear atypia, mitosis and
vascular proliferation and
4 (three or four criteria: usually
the above and necrosis and or endothelial proliferation).
the histological grade of astrocytic tumors, communication is often
simplified by use of of the terms' low grade astrocytoma', 'anaplastic
astrocytoma', and 'glioblastoma mutiforme'. Despite
variability among the grading systems, the distinction between low grade
astrocytoma, and anaplastic astrocytoma is commonly made based on the
presence of mitoses and increased cellularity. Similarly, glioblastoma
multiforme and anaplastic astrocytoma are frequently
distinguished based on the presence
of necrosis and endothelial proliferation.
variants of astrocytoma may display both age and location related
For example, the majority of pilocytic astrocytomas occurs in childhood
population and involves the cerebellum.
A tendency to the diagnosis of higher tumor grades is
found with increasing patient age. This is reflected by the presence of
incidences for low grade astrocytoma,
and glioblastoma multiforme during the
third, fourth, and fifth decades of
life, respectively. Further, the overall incidence of astrocytomas,
regardless of grade, is seen to rise proportionately with age, peaking
during the fifth to sixth decades of life.
Clinical features of this condition commonly include headaches,
papilledema, and blurred vision. Symptoms such as these are
of limited value for predicting tumor
location, although they may play a valuable role in prompting patients to
seek medical attention.
symptoms experienced by patients with astrocytomas
are primarily determined by the location and size of the tumor involved.
Supratentorial lesions present with seizures and focal neurological
deficits, such as, dysphasia and hemiparesis.
In cases involving the posterior
fossa, ataxia, dysmetria,
and nystagmus, are frequently found. Astrocytomas
involving the brainstem are often notable for the
production of a variety of symptoms,
including cranial nerve deficits and limb weakness. in the presence
of large tumors or obstructed cerebrospinal fluid (CSF) circulation,
evidence of increased
intracranial pressure may be seen.
In general magnetic resonance
imaging is superior to computerized tomography to evaluate their
composition and relationships with nearby anatomical structures.
Conversely, CT is more sensitive
for revealing characteristics such
as hemorrhage and intratumoral calcification. Despite the excellent
radiographic methods available,
however, imaging studies are
often unreliable for discriminating among the individual
historical grades and variants of
The use of post operative imaging (within 48 hours), particularly MRI with
gadolinium, is invaluable is assessing completeness of resection and
anaplastic astrocytoma, and glioblastoma are regarded as a spectrum of
diffuse astrocytic tumors with common molecular genetic abnormalities.
presence of multiple characteristic
genetic mutations, whether
inherited or acquired, has
been associated with the oncogenesis of astrocytomas. Some have
also theorized that the accumulation
of specific genetic mutations brings about the further progression
of low grade neoplasms to higher
degrees of malignancy. For
example, deletion mutations of chromosome 17 (17p)
and, less frequently, chromosome 22
(22q), are known to be present among a large number of
astrocytomas regardless of grade. Other mutations 13 (13q), 9 (9p), and
reflecting later transformative events. Moreover, deletion mutations of
chromosome 10 (10q) are found almost exclusively among glioblastomas,
suggesting that they are involved in the transition to the highest grades
astrocytic tumors, the transition to glioblastoma is associated with
upregulation of the epidermal growth factor receptor (EGFR) gene found on
chromosome 7. It has been
proposed that mutation common to high grade astrocytomas
specifically that of chromosome 10q may be involved in the stimulation of
EGFR gene expression or the
disinhibition of its regulation.
interest has been generated in utilizing the presence of these
characteristic genetic alterations for the purpose of predicting
aggressive tumor behavior. In the future, the use of
techniques is likely to
play an increasing role
in the treatment of neoplasms, such as the astrocytoma.
Low grade Astrocytoma:
term 'low grade astrocytoma’ is given to a group of astrocytic tumors with
a relatively well-differentiated
histological appearance. Among these are included typical
low grade astrocytoma, pilocytic astrocytoma, pleomorphic
xanthoastrocytoma, and subependvmal giant cell
astrocytoma. Although strictly intended to imply uniform
astrocytic cell composition, low grade neoplasms
oligodendroglioma-astrocytoma cell content
are also occasionally included in
Pilocytic and low-grade
astrocytomas are encountered most frequently,
accounting for 43% of astrocytomas
as a whole.
median age of patients with low grade gliomas is approximately 35 years.
There is a biphasic age distribution, with two peak incidences at 6 to 12
years, and 26 to 46 years, with a slight male preponderance.
low grade astrocytomas in adults arise supratentorially; half are of
typical histology, with the remaining
consisting of pilocytic astrocytomas and mixed
oligodendrogliomas-astrocytomas in nearly equal proportions.
Involvement of the hemispheres is more common
than that of deeper structures, such as the basal
ganglia and brainstem.
When hemispheric in location, frontal lobe involvement is more prevalent
than temporal or parietal lobe involvement.
Infratentorial lowgrade astrocytomas occur most
commonly in the cerebellum of children. Whereas low grade cerebellar
astrocytomas account for 15% to 18%
of all intracranial tumors among children, they account for only 1% of
those among adults. The pattern of cerebellar involvement
is unihemispheric in approximately
30%, bihemispheric in 34%, and vermian in 16%
of cases. Histologically, the vast majority, approximately
85% of lowgrade cerebellar astrocytomas are pilocytic.
For practical purposes,
pilocytic astrocytomas are commonly given separate consideration
from typical low grade astrocytomas
as they have been associated with a more
addition to the cerebellum, pilocytic astrocytomas
commonly involve the hypothalamus and optic pathways,
constituting the majority of tumors referred to as
hypothalamic and optic gliomas.
diagnosed during the first two decades of life
are predominantly cerebellar. In contrast, those found in
adults are most often supratentorial. When located
temporal lobes, frontal lobes, and
basal ganglia are most commonly involved. Pilocytic astrocytomas
are typically diagnosed earlier in life than
low grade astrocytomas, with mean
ages ranging from 14 to 18
years, and from 30 to 37 years,
Signs and symptoms
observed at the time of diagnosis
are primarily related to tumor location. 60% of them present with
seizures, twice as frequently as the high grade ones. They are one of the
common causes of intractable epilepsy.
The CT characteristics of typical low-grade astrocytomas
are those of a poorly defined, hypodense mass.
Unlike high grade astrocytomas, less evidence of mass effect,
surrounding edema, and heterogeneity is present.
On MRI, these
tumors are hypo to isodense on T1 and hyperdense on T2 images.
Enhancement is variable
or absent on both CT and MRI. Calcification and cytic changes are not
rare. In comparison,
pilocytic astrocytomas have clearly defined borders
and are further distinguished by their tendency to enhance, faintly
Cystic Pilocytic astrocytoma-MRI
(with mural nodule)
(well defined borders
and no edema)
Low grade astrocytoma- MRI
(ill defined borders)
Other recent advances in
neuroimaging help for further evaluation.
Fibrillary Astrocytoma (H&E)-
moderate increase in cellularity by neoplastic astrocytes with
enlarged nuclei and coarse chromatin. Cytoplasmic processes
are indistinct in a finely fibrillary
Gemistocytic Astrocytoma (H&E)-
distinct cells with large eosinophilic, slightly angulated
cytoplasm and eccentric nuclei.
On gross examination, low grade astrocytomas are typically poorly
circumscribed and may be similar in appearance to the surrounding non
On histological examination, mildly increased cellularity
and slight pleomorphism are present, but notably absent are changes such
as mitosis and extensive atypia, which
are characteristic of high-grade astrocytomas. On microscopic
examination, fibrillary astrocytes are most often
observed, though multiple astrocytic morphologies may also be present.
Neoplastic cells can be seen to diffusely
infiltrate surrounding tissues. Nonneoplastic
tissue elements may become incorporated, or trapped within the tumor mass.
This phenomenon may on occasion give false impression of mixed tumor.
astrocytomas are composed of a
biphasic cellular pattern consisting of bipolar "piloid"
cells with multiple, long fibrillary processes and microcystic
structures made up of sparsely fibrillated protoplasmic
astrocytes. Also characteristic of pilocytic astrocytomas
is the presence of eosinophilic structures, seen as intracytoplasmic
globules or as long extracellular fibers. These structures have been
termed ‘granular bodies’ and ‘Rosenthal fibers’ respectively.
Evidence of malignant changes,
such as atypia and endothelial
can frequently be seen. Unlike the situation for typical low grade
astrocytomas, the presence of these changes does not necessarily
predict aggressive neoplastic behavior.
Key features include
and/or eosinophilic hyaline granules.
of low grade gliomas continues to be controversial. All treatment
options, including radiotherapy immediately after surgery,
radiotherapy only for incomplete resected gliomas, and radiotherapy at
recurrence or progression, are considered valid options, and none is
supported by a randomized controlled study.
of Rosenthal fibres(arrow) and granular eosinophilic
bodies are seen along
with fibrillary fasicles.
consider a complete resection to be curative
for pilocytic astrocytomas with the use of postoperative irradiation
offering little additional benefit. furthermore, some have advocated
withholding radiation treatment, even if subtotal resection is obtained
initially, reserving radiation for tumor recurrence or surgery limited
timing and extent of resection is controversial. A similar argument has
been made for the treatment of
typical low grade astrocytomas in both
children and adults.
Restrictions on the
use of radiation treatment among
young children have been recommended due to high degree of associated
morbidity. Additionally, some have implicated radiation as a cause
of the mutational events leading to increased aggressiveness. Despite
this, some have found post operative radiation useful in
typical low-grade astrocytomas, even
in cases of total resection. Still
others have argued that the benefit of completely resecting typical
low grade astrocytomas remains
unproven, instead advocating the use of focused radiation therapy alone as
use of chemotherapeutic agents for the treatment
of low grade astrocytomas is controversial, with studios citing little
improvement over the results achieved with conventional therapies alone.
These studies have recommended
reserving chemotherapeutic agents for cases of
inoperable low grade
astrocytomas or as a means of
obviating the morbidity associated with cerebral irradiation in children.
The prognosis for patients with low grade astrocytomas varies with
tumor location and histology.
Regardless of supra or infratentorial location, pilocytic tumors are
associated with the most favorable prognosis, with
5 and 20 year survival rates of 85% to 86% and 79% to 82%.
Although varying with supra and infratentorial location,
the prognosis for other
low grade astrocytomas is much less favorable.
Those in a
supratentorial location have been found to
carry 5 and 10 year survival rate of
51% to 56% and 23% to 39% respectively.
In contrast, those occurring in the
cerebellum are associated with still poorer outcomes, with survival rates
at both 5 and 10 years of 7%.
the microcystic change is recognized to be a regressive feature and indeed
one does not witness much cellular activity in such regions. The cytoplasm
is scanty and fibrillar and the nuclei small and monomorphic. Another
feature of slow growth and thus seen in low grade astrocytomas is the
formation of thick smooth cytoplasmic extensions of glial cells, called
Rosenthal bodies. They were believed to represent degenerating astrocytes.
Other factors predictive of improved outcome include younger age, seizure
at presentation, and lack of preoperative fixed neurological deficit.
recurrence is often associated with malignant
progression and is a common cause of mortality among patients with low
The frequency is thought to be highest among patients with
typical low grade astrocytoma, occurring in 57% to 72%
of cases. Factors that have been associated with an increased rate of an
increased rate of recurrence include subtotal resection and the presence
of oligodendroglial tumor components. additionally, some believe that
malignant progression of low grade astrocytomas is more prevalent among
for the low grade astrocytomas focus on developing chemotherapy regimens
that control tumor growth with fewer side effects on other organs of the
body. Because these tumors grow slowly, the strategy is to give less
intensive chemotherapy over long periods of time.
For older children and
those whose tumors progress despite chemotherapy, new radiation techniques
are under study to “focally” deliver therapy with minimal effects on the
cell astrocytoma (SEGA):
Pleomorphic Xanthoastrocytoma (PXA):
are rare(<1%), typically, develops in children and young adults.
Invasion of the overlying dura in superficial lesions is common.
may be eroded. Temporal lobe is the commonest site, followed by the
parietal, occipital, and the frontal lobes.
history of chronic seizures and headaches is the usual presentation.
MRI, T1 images reveal, an iso to hypodense lesion with cystic and
calcified changes. Uniform contrast enhancement of the tumor nodule
with typically non enhancing cyst wall is seen. On T2 it is hyperdense.
Gross total excision, if possible, is advised. The cyst wall need not
be removed. The role of adjuvant therapy following a subtotal
resection or in those with high mitotic index is not clear at present.
Resurgery for recurrent or progressive lesions followed by radiation
Histologically, there is closely packed, highly pleomorphic, giant
and multinucleated cells. Variable xanthomatous change is seen in the
cytoplasm. Prominent eosinophilic granular bodies are constant.
Mitosis is rare. In children, it may mimic a GBM.
immunohistochemistry days, it was classified as histiocytic fibromas.
Some still call it gliofibroma and group this along with
gangliogliomas and infantile desmoplastic gliomas.
astrocytic nature is demonstrated by GFAP immunopositivity.
outcome is generally good. Local recurrence may occur.
of the cases recur and undergo malignant change into GBM.
PXA (H&E) -
giant often multinucleated neoplastic astrocytes
with spindle cells, and
Anaplastic astrocytomas account for approximately 12% to 34% of high
astrocytomas. Their peak incidence occurs during the fourth to early
fifth decades of life, falling between that of low grade astrocytomas
and glioblastoma multiforme.
They are also
intermediate among astrocytomas
with respect to histology. While distinguishable from low grade
astrocytomas on the basis of their increased cellular density, greater
degree of nuclear atypia, and mitoses, they lack the endothelial
proliferation and necrosis characteristic of glioblastoma multiforme.
imaging reveals better defined borders than that of low grade ones;
they appear hypo to iso dense on T1 and hyperdense on T2 MRI images.
Greater the contrast enhancement, and edema suggest a higher grade,
and unlike glioblastoma, the enhancement is homogenous.
Anaplastic astrocytomas are
particularly susceptible to histological misclassification,
often being diagnosed as glioblastomas.
confusing is the
finding that low grade astrocytomas with a gemistocytic astrocyte
content in excess of 60% behave with an aggressiveness similar to that
of anaplastic astrocytomas and often treated as anaplastic.
astrocytomas have a more circumscribed appearance than the
low grade astrocytic tumors, but friable, granular, and
grayish. They are prone to hemorrhage.
However, this appearance
is deceptive as neoplastic elements can still be found to
infiltrate surrounding tissues. Microscopically, neoplastic cells can
be variably small, large, stellate, pilocytic, etc.
Key feature is
usually mitotic figures.
(more homogeneous contrast
enhancement than GBM)
Anaplastic Astrocytoma (H&E)-moderate
to marked increase in neoplastic cellularity(arrow),
cellular pleomorphism, & mitosis(double arrow).
The median survival for patients diagnosed with anaplaslic
astrocytoma ranges from 15 to 28 months, with projected 1, 2, and 5 year
survival rates of 60% to 80%, 38% to 64%, and 35% to 46%, respectively.
Aggressive resection has shown higher survival; some have found little
improvement with radical excision and place a greater emphasis on the
radiotherapy and chemotherapy.
use of postoperative radiation has been shown to prolong survival
in patients with anaplastic astrocytomas, often to a greater degree than
when used for the
treatment of glioblastoma multiforme. In addition,
some authors have advocated the use of alternate
treatments, such as brachytherapy, radiosensitizers, and chemotherapeutic
agents both initially and at recurrence.
However, others have found these alternate modalities to be of
little extra benefit and rely more heavily on conventional forms of
For high grade tumors,
new approaches on trial, include use of new chemotherapy drugs,
high doses of chemotherapy following radiation therapy, and gene therapy
to make the tumor cells more sensitive to chemotherapy. A major problem in
treatment is that the high dose chemotherapy also kills cells in the bone
marrow that produce healthy blood. This raises the risk of severe
infection and slows down the delivery of chemotherapy. Gene therapy
approaches are being developed to protect bone marrow from these side
effects so that chemotherapy can be given more intensively to fight the
rapid tumor growth.
and immunotherapy are still under in the experimental stage.
As with other astrocytic tumors, primary site recurrence
is the most common cause of mortality.
thought to correlate with improved outcome
in patients with anaplastic astrocytoma include younger age, higher
preoperative performance scores, and presentation with seizures.
Additionally, some have
found improved outcomes among patients previously
diagnosed with lower grade astrocytic tumors in comparison
to patients in whom an anaplastic astrocytoma
has arisen de novo.
Glioblastoma multiforme (GBM):
First recognized by Virchow, in 1863,
and described later as 'spongioblastoma multiforme', this, the most
malignant neoplasm in the human body.
Glioblastoma multiforme is the least differentiated and most aggressive
form of astrocytoma.
It accounts for 15% to 23% of all primary intracranial tumors.
Furthermore, it constitutes 35% of gliomas, 66% to 87% of high grade
astrocytomas, and 50% of all astrocytomas, making it the most common
Patients diagnosed with glioblastoma multiforme are most commonly in their
fifth or sixth decade of life.
The diagnosis is made less frequently in younger age groups and rarely in
children, where GBM account for less than 9% of all
intracranial primary tumors.
Regardless of age, hemispheric location is most common.
The presence of multifocal tumors is thought to occur in 2/3% to 9% of
Headaches due to raised ICT, and focal
neurological deficits according to the site of location are the common
presenting symptoms. Unlike in low grade gliomas, seizure as a
presenting symptom is uncommon.
On CT and MRI, the GBM appears as a well defined mass
with heterogenous contrast enhancement and extensive parenchymal
edema. A characteristic irregular rim of high intensity (due to florid
endothelial/vascular proliferation), may simulate metastasis or an
(with rim of heperdensity
Most GBMs contain a centrally located, hypoxic area of necrosis that
develops as the tumor mass outgrows its blood supply. This hypoxic zone is
concentrically enveloped by hypercellular neoplastic tissue and
surrounding edematous white matter.
The more malignant astrocytomas have been found to have features
histologically indistinguishable from glioblastoma multiforme and thus
there is a a controversy against assigning a separate name for this tumor,
as there is no such cell as a glioblast.
|However, it must be
admitted that a percentage of glial tumors present themselves with
such a very rapid onset of signs and symptoms, that either at surgery
or autopsy there is no clear trace of an astrocytoma and all parts of
the tumor show merely the characteristic pleomorphism of a
the tumor is highly cellular with closely packed cells exhibiting a
varying degree of pleomorphism. The cells vary in size and shape;
large bizarre giant cells with many nuclei are frequently seen, as
also hyperchromatism, mitotic figures and abnormal nuclei. Another
striking feature is the presence of vast areas of necrosis ringed
closely by growing spongioblasts giving rise to an appearance of
pseudopalisading. Mononuclear cuffing of blood vessels and
endothelial proliferation, constitute further histological evidence of
a higher degree of malignancy. The malignant astrocytomas, in
particular, tend to spread along the meninges after reaching the
surface, and along the blood vessels after entering the Virchow-Robin
Glioblastoma multiforme- Pseudo
palisading(arrow) of tumor cells around a central
zone of necrosis(double arrow)
WHO currently recognizes two histological variants
giant cell glioblasloma in which a predominance of multinucleated
giant cells is seen, and gliosarcoma (a
term originally used by Stroebe, in 1895)
or Feign tumor, where malignant neoplastic induction of
vascular stromal elements is present.
mesodermal tumor from either the meninges of the blood vessels was
believed to stimulate a vigorous proliferative and hyperplastic
reaction of the surrounding neuroglia which acquire malignant
features. Protagnonists of this latter theory are few and it is
generally thought that the pronounced vascular proliferation is
responsible for a gliosarcoma. These tumors macroscopically may
sometimes resemble meningioma and even histologically a diagnosis of
mesenchymal tumor may be made if the sampling of the tissue is not
representative. Because of the presence of mesenchymal elements,
extracranial metastasis is possible from such neoplasms.
Management, currently recommended, is an aggressive
if possible, and post operative irradiation as the initial form of
Attempts to achieve an aggressive resection may, however, be limited
when patients are poor surgical
(with subcutaneous extension)
candidates or have tumors that involve eloquent or deep structures.
Alternate modalities are needed in such cases.
Reoperation for recurrence in selected patients who have had favorable
results to initial treatment may be considered.
Postoperative radiation has been found to be helpful.
Radiotherapy, age, and
performance status have been demonstrated to be the three most significant
Usual total dose is 60
Newer techniques, such as, dose fractionation, stereotactic radiotherapy,
heavy particle radiotherapy, and brachytherapy have also been used with no
evidence to suggest a better outcome.
As compared to radiotherapy, role of
limited. However, it is currently used in the young and in recurrence
chemotherapy has been a nitrosourea based regimen. Newer promising
chemotherapy includes Temozolomide and CPT-11.
Newer therapies, such as,
and immunotherapy are
for patients with glioblastomas have shown little improvement despite
the use of multiple treatment modalities, including surgery, whole brain,
local, and focused radiation( brachytherapy); radiosensitizing
agents, and other forms of chemotherapy have not helped. Median
life expectancies of 8 to 10 months after diagnosis
are common, along with 1, 2, and 5-year survival
rates of 30% to 44%, 10% to 12%, and 2.5% to 5% respectively.
Survival rates cited for children are similar
to those for adults.
The most common cause
of mortality among patients with
glioblastoma regardless of age is recurrence.
Younger patients with seizures at presentation, lack of focal neurological
deficit, and complete tumor resection favor a better prognosis.
using the term "complete resection," the propensity for astrocytomas
to disseminate must be taken
into account. Microscopically, local dissemination is reflected
by the presence of neoplastic cells that often infiltrate 1 to 3 cm
into adjacent tissues despite a well-circumscribed
appearance upon gross inspection.
In addition, more extensive spread occurs preferentially along
sub cortical white
mater tracts (corpus callosum, uncinate fasciculus, auditory and
visual bundles, corona radiata, subependymal route, CSF
dissemination, along blood vessels & perivascular spaces, and sub pial
frequently giving rise to
nearby tumor foci.
spread may therefore take place by virtue of extension through corpus
callosum giving rise to characteristic ‘butterfly’ pattern seen on CT/MRI
can be categorized as 'Connected (microscopic parenchymal connection
satellite lesions) or
Disconnected (no detectable microscopic connection)', and as 'Synchronous
(if present on initial presentation) or Metachronous (if developed during
follow-up. They are termed multiple, if present at the same time but are
separate spatially, and multicentric, if they are independent spatially as
well as temporarily.
multiple astrocytomas may arise independently within a single patient, the
majority are probably represent the presence of a single neoplastic
Reportedly, the multifocality occurs in 2.3% to 9.1% of cases.
has more infiltrative growth than does GBM thus multifocal glioma occur
more frequently in AA than GBM.
for tumor cell attachment & migration are - myelin, ECM protein, Merosin,
Diffuse subarachnoid dissemination of intracranial tumors is termed
leptomeningeal gliomatosis. This condition often results from the presence
of a high grade intracranial neoplasm that has gained access to the CSF by
virtue of its proximity to the
cisterns. In such cases, patients
may experience a variety of symptoms, including mental status
changes, headache, cranial nerve
deficits, and back pain.
Diagnosis is by CSF cytology. Radiology may
Therapeutic measures employed include craniospinal radiation, and systemic
or intrathecal chemotherapy. Survival rates are generally poor and
primarily related to histology of the and its responsiveness
to treatment. With respect to astrocytic tumors, limited
success has been achieved in the treatment of leptomeningeal gliomatosis
involving anaplastic astrocytomas.
However, the prognosis for patients with leptomeningeal gliomatosis
resulting from GBM is bleak,
with survival rates generally
measured in terms of weeks.
Among adults, astrocytomas have the distinction of being
the intracranial neoplasm most likely to metastasize
outside the CNS.
However, even with astrocytomas, metastasis is rare. The extraneural
presence of metastases is frequently associated with previous craniotomy
or a diversionary shunting procedure. It is by virtue of these routes the
metastatic cells are believed to gain access to extradural lymphatic and
vascular tissues. However, a prior dural disruption is not strict
requirement. These cases are a result of invasion of intracranial vascular
structures, such as venous sinuses.
The most common sites for extraneural metastases include lung, lymph
nodes, and bone.
In those who have had shunt procedures done, the abdomen should also be
considered a potential site.
The probablity of metastases appears to be related to the degree of tumor
anaplasia, with GBM more likely to metastasize than others. Survival rates
for such patients are poor,
ranging from 6 months to
2 years after the time of diagnosis.
Chemotherapy, although of minimal benefit to survival, is advised to
improve the quality of life.