a healthy 15-year - old woman was admitted to the department of neurosurgery of our institution with a chief complaint of a 1-month history of headache and dizziness . 1 ) demonstrated a 6.85 cm - sized , solid and cystic intra - axial mass in the right temporooccipital area , compressing the posterior horn of the right lateral ventricle . the solid portion of the mass included a calcification , thus presumably partly infiltrating into the brain parenchyma . differential diagnoses based on radiology include astroblastoma , ependymoma , pleomorphic xanthoastrocytoma and supratentorial primitive neuroectodermal tumor . postoperatively , the patient received a focal fractionated radiotherapy with a total dose of 5,040 cgy . a follow - up mri was taken on postoperative month 5 , which revealed no recurrence or progression of the tumor . most of the small- to medium - sized cells with papillary structures had hyperchromatic nuclei and coarse chromatin . they had a round - to - oval shape and contained hyperchromatic nuclei , eosinophilic cytoplasm and prominent eosinophilic intranuclear inclusions . considering the cytologic features along with the clinical and radiological data , we made an intraoperative frozen diagnosis of ependymoma . with a retrospective review of the slides , we identified a perivasculasr pseudorosettes - like lesion . the surgical specimens consisted of multiple pieces of soft red - to - grey tissue . then , the specimens were sectioned at a thickness of 2 m and then stained with a hematoxylin and eosin dye . for immunohistochemistry , we used antibodies against glial fibrillary acidic protein ( gfap ) , epithelial membrane antigen ( ema ) , cytokeratin , ki-67 , synaptophysin , and cd99 ( mic2 ) . 3 , a histopathologic examination showed that the tumor had perivascular pseudorosettes ; this is one of the characteristic features of ependymoma . the tumor cells had histopathological findings that are consistent with squash smear ones described above . this was also accompanied by the frequent presence of bizarre pleomorphic giant cells with prominent intranuclear eosinophilic inclusions . according to the who criteria , it had features of an anaplastic tumor , including a marked cellularity , abundant mitoses , vascular proliferation and necrosis . that is , it had a high intensity , a dot - like expression of cd99 and that of ema . in addition , the tumor cells had a ki-67 labeling index of about 10% ( fig . a rare variant of ependymoma , gce poses a diagnostic challenge for the pathologists on the intraoperative frozen section as well as the permanent section . but pseudorosettes are not present in all the case of gce . according to zec et al.,2 who first described two cases of gce in 1996 , the absence of perivascular pseudorosettes in gce might reflect the failure of the neoplastic cells to elaborate perivascular process . this often leads to the misdiagnosis of gce as glioblastoma multiforme,11 anaplastic astrocytoma,6 subependymomal giant cell astrocytoma or tanycytic ependymoma5 on intraoperative frozen section . in addition , gce should also be differentially diagnosed from anaplastic oligodendroglioma , clear cell ependymoma , pleomorphic xanthoastrocytoma and giant cell glioblastoma.10 despite these diagnostic challenges , there has been an increase in the demand for rapid intraoperative diagnosis . this is particularly case with the neurosurgical practice . a simple , reliable , and rapid method , the squash smear technique is useful to present detailed cytologic features of lesions . it is useful in making an intraoperative diagnosis of central nervous system lesions.14 to our knowledge , however , there are no reports about the cytologic features of gce . we performed a review of literatures about gce , focusing on the cytologic features seen on the tissue sections , whose results including our case are summarized in table 2 . the cytologic features are classified based on the cellularity , hyperchromatic nuclei , binucleation or multinucleation , eosinophilic cytoplasm , intranuclear inclusion / pseudoinclusions , perivascular pseudorosettes , brisk mitosis , necrosis and fibrillary background . basically , all the 14 cases showed hypercellularity , mitosis and necrosis . of the total cases , 93% ( 13/14 ) had eosinophilic cytoplasm and perivascular pseudorosettes ; 71% ( 10/14 ) did hyperchromatic nuclei ; 57% ( 8/14 ) did intranuclear inclusions / pseudo - inclusions ; and 50% ( 7/14 ) did binucleation or multinucleation . it is noteworthy , however , that these features are based on tissue sections of gce rather than cytology specimens such as the squash smear preparations . it is , therefore , a matter of course that there is no consistency in the cytologic features between the tissue sections and the cytology specimens . in our case , there were perivascular pseudorosettes on the tissue sections , but not found on the squash smear preparations . but both diagnostic modalities showed such findings as mitosis and necrosis , giant cells and intranuclear inclusions / pseudoinclusions . further comparative descriptions are warranted to define the cytologic features of gce between tissue sections and cytology specimens . in making an intraoperative frozen diagnosis based on squash smear preparations featuring the mitosis and necrosis , as well as the high cellularity , and the presence of giant cells showing hyperchromatic nuclei with eosinophilic cytoplasm and intranuclear inclusions / pseudoinclusions would be key histologic features that are helpful for establishing a diagnosis of gce . this is particularly true to our case ; the presence of giant cells with intranuclear inclusions and papillary structures was a critical clue to intraoperative frozen diagnosis . in addition to the cytologic features , the clinical and radiologic findings are helpful for improving the diagnostic accuracy . due to a relatively smaller number of reported cases , we failed to establish the relationship between the histological pattern of gce and its prognosis . in patients with anaplastic gce , however , a poor prognosis is expected with a relatively higher rate of recurrence ( table 1 ) . in our patient , there was no disease progression or recurrence . due to a shorter length of follow - up , however , further long - term follow - up studies are warranted to predict clinical outcomes of anaplastic gce
here , we present a case of anaplastic giant cell ependymoma ( gce ) occurring in a 15-year - old woman . 
 squash smear slides for intraoperative frozen section diagnosis revealed oval to round cell clusters with a papillary structure in a fibrillary background . 
 this was occasionally accompanied by the presence of bizarre pleomorphic giant cells with hyperchromatic nuclei and prominent intranuclear inclusions . 
 these intranuclear inclusions were a key clue to diagnosis of ependymoma . 
 histologic analysis revealed features of a high - grade tumor with perivascular pseudorosettes and bizarre pleomorphic giant cells , which established the diagnosis of gce . 
 we performed a review of literatures about the cytologic features of gce , including our case , thus proposing that intraoperative frozen diagnosis of gce would be established by squash smear preparations featuring the mitosis and necrosis , as well as the high cellularity , and the presence of giant cells showing hyperchromatic nuclei with eosinophilic cytoplasm and intranuclear inclusions / pseudoinclusions .