astroblastoma is a rare glial tumor occurring predominantly in the cerebral hemispheres of young adults .
it is difficult to determine exact number of astroblastoma cases since the number may include some that are not typical astroblastoma .
however in some report it was estimated that only 0.45 - 2.8% of all neuroglial tumors were astroblastoma ( 2 ) .
similar perivascular pseudorosettes may also occur partly in gemistocytic astrocytoma , anaplastic oligodendroglioma , anaplastic astrocytoma , glioblastoma , etc .
therefore , the term , astroblastoma , must be used only for the cases in which typical histological findings are observed throughout the tumor ( 3 ) .
a 15-yr - old female patient had presented with headache and diplopia for one year and six months , and her headache in the area of right frontal lobe had become worse for the last month .
brain mri showed a well demarcated mass , 9.7 cm in diameter , in right frontal lobe .
after an injection of gadolinium , the tumor showed an inhomogenous enhancement . within the tumor
tumor cells were aligned along the fibrovascular stalk by one or two cell layers , but in some areas it was multilayered .
perivascular pseudorosettes became prominent in areas where the tumor cells were separated by artifacts ( fig .
cytoplasmic processes were short and thick , of which blunt footplates were attached to the vessels ( fig .
most tumor cells showed nuclear monotony with less atypism , yet a small number of them showed mild nuclear atypia .
vascular hyalinization or sclerosis was observed in some areas , but no endothelial proliferation was found ( fig .
areas of anaplastic astrocytoma , gemistocytic astrocytoma , and glioblastoma were not found in any part of the tumor .
cytoplasmic processes of tumor cells composing perivascular pseudorosettes showed strong positive reaction for glial fibrillary acidic protein ( gfap ) ( fig .
the tumor cells showed diffuse strong positivity for s-100 protein , vimentin and neuron specific enolase ( nse ) , and focal positivity for epithelial membrane antigen ( ema ) and cam 5.2 ( fig .
the tumor cells were negative for synaptophysin , neurofilament protein ( nfp ) , pan - cytokeratin , high molecular weight keratin ( hmwk ) immunostains .
mib-1 labeling index accounted for 8.0% ( 83/1,000 ) , and p53 positivity was 16% ( 159/1,000 ) ( table 1 ) .
six weeks after the operation , radiation therapy of 4,500 cgy was performed for a period of seven weeks .
three years and nine months after the operation visual acuity decreased slowly and the left hemiplegia developed progressively .
multiple low intensity lesions was observed in t1-weighted image , and they were considered as radionecrosis .
since bailey and bucy reported on astroblastoma for the first time in 1930 , the existence of the tumor itself has been one of the most interesting subjects ( 4 ) .
however , from the middle of the 1980s up until today , astroblastoma has been reported as a distinct entity ( 1 , 5 - 9 ) .
the patients ranged from 1 to 58 yr old ( average , 16 yr ) ( 1 , 8 , 9 ) .
astroblastoma develops usually in cerebral hemisphere , but it can develop in the corpus callosum , cerebellum , optic nerve , brain stem , or in filum terminale ( 7 , 11 ) . in cerebral hemispheres , astroblastoma usually develops in cortex , subcortical area , and periventricular area , but not in the ventricle itself ( 11 ) .
different from the perivascular pseudorosettes in ependymoma , those in astroblastoma have short and thick cytoplasmic processes .
the cytoplasmic processes have blunt - ended footplates and are attached to basal lamina of blood vessels . in less cellular areas ,
typical perivascular pseudorosettes are observed even in the areas where tumor cells show solid growth patterns .
the blood vessels frequently show hyalinization and even sclerosis ( 1 , 3 , 8 , 10 , 11 ) .
astroblastomas are classified into low grade and high grade according to histological findings ( 8) .
the high grade astroblastomas show increased cellularity with multiple cell layers upon the vascular walls .
immunohistochemically , the tumor cells showed positivity for gfap , s-100 protein , vimentin , nse and ema coinciding with the findings in other reports ( 2 , 6 , 12 - 14 ) .
the fact that neoplastic astrocytes may be positive for nse and ema is well known ( 12 ) .
however , reactions to cam 5.2 reported as negative ( 2 , 11 , 12 ) or partly positive ( 13 ) .
the term ' astroblastoma ' is misleading in itself , since this tumor is not overtly astrocytic , nor are they ' blastic ' ( 1 ) . bailey and bucy believed that astroblastoma originated from astroblast , an intermediate stage between glioblasts and astrocytes ( 4 ) .
however , in a study by means of electron microscope it was proved that tumor cells of astroblastoma are intermediate between astrocytes and ependymal cells , and thus a possibility of tanycytes is presented as the origin of astroblastoma ( 7 , 13 , 15 ) .
tumors showing histological findings similar to astroblastoma are ependymoma , papillary meningioma , choroid plexus tumor , etc .
ependymoma is usually a well - demarcated mass and forms perivascular pseudorosettes , which may be confused with astroblastoma .
it also shows positivity for gfap , s-100 protein and vimentin and even focal positivity for cytokeratin , as astroblastoma does . however , perivascular pseudorosettes in ependymoma have thin and long cytoplasmic processes with no foot plates , which are different from the pseudorosettes of astroblastoma . and anuclear fibrillary zone is well developed around the blood vessels .
tumor cells between perivascular pseudorosettes are compact and show small ovoid monotonous nuclei with fine chromatin pattern .
papillary meningioma has perivascular papillary or pesudopapillary pattern with structures similar to pseudorosettes of ependymoma .
the tumor cells of papillary meningioma show positive reaction for cytokeratin and negative reaction for gfap .
in addition , papillary meningiomas usually show connection to meninges as well as typical meningioma areas .
choroid plexus tumor also shows papillary growth pattern , which may be confused with astroblastoma .
immunohistochemically choroid plexus tumor shows strong positivity for cytokeratin , while negativity or focal positivity for gfap , and characteristic transthyretin positivity ( 16 , 17 ) .
the natural history of the astroblastoma seems to place it between the astrocytoma and glioblastoma ( 8) . the low - grade astroblastomas are thought to have better prognosis than the high - grade astroblastomas .
anaplastic histology has been associated with recurrence and progression , suggesting the more aggressive treatment , including radiotherapy , is necessary for high - grade lesions ( 1 , 8 , 9 , 16 ) .
 astroblastoma is one of the very unusual type of tumors , whose histogenesis has not been clarified . 
 it occurs mainly among children or young adults . 
 astroblastoma is grossly well - demarcated , and shows histologically characteristic perivascular pseudorosettes with frequent vascular hyalinization . 
 perivascular pseudorosettes in astroblastoma have short and thick cytoplasmic processes and blunt - ended foot plates . a 15-yr - old girl presented with headache and diplopia for one and a half year . 
 a well - demarcated mass , 9.7 cm in diameter , was found in the right frontal lobe in brain mri , and it was a well - enhanced inhomogenous mass . 
 cystic changes of various sizes were observed inside the tumor mass as well as in the posterior part of the mass , but no peritumoral edema was found . 
 histologically , this mass belongs to a typical astroblastoma , and no sign of anaplastic astrocytoma , gemistocytic astrocytoma or glioblastoma was found in any part of the tumor . 
 immunohistochemically , the tumor cells showed diffuse strong positivity for glial fibrillary acidic protein , s-100 protein , vimentin and neuron specific enolase , and focal positivity for epithelial membrane antigen and cam 5.2 , while showing negativity for synaptophysin , neurofilament protein , pan - cytokeratin and high molecular weight keratin . 