ewing 's sarcoma family of tumors are a group of small round - cell neoplasms , which include ewing 's sarcoma ( ews ) , primitive neuroectodermal tumor ( pnet ) , askins tumor , pnet of the bone , and extraosseous ewing 's sarcoma ( ess ) .
ewing 's sarcoma / peripheral primitive neuroectodermal tumor , presumed to be neuroectodermal in origin , most often occurs in the bone and soft tissues of children and young adults .
the intracranial extraosseous ewing 's sarcoma ( cns - ess ) is extremely rare and often misdiagnosed as central nervous system pnet ( c - pnet ) or as other primary intracranial neoplasms .
an 11-year - old female presented with a history of headache for one year , which increased in intensity over the last one month .
she had repeated episodes of vomiting for one month and a left temporal scalp swelling , which was gradually increasing in size .
on examination there was bilateral papilledema , but no other focal neurological deficits were detected .
the left temporal scalp swelling was mildly tender , firm , immobile , and non - pulsatile with ill - defined margins .
the computed tomography scan ( ct scan ) of the brain showed a rounded , well - defined , heterogeneously hyperdense , enhancing lesion in the left temporoparietal region , with a mass effect and destruction of the left temporal bone , extending into the scalp , suggesting the possibility of a meningioma .
no evidence of calcification was noted within the lesion   [ figure 1 ] . magnetic resonance imaging ( mri ) of the brain showed a left temporal lesion , hypointense on t1 , heterointense on t2 , with heterogeneous enhancement [ figure 2 ] .
a significant mass effect was detected with a midline shift to the right , of 15 mm .
preoperative ct scan of the brain showed a rounded , well - defined , heterogeneously hyperdense , enhancing lesion in the left temporoparietal region , with a mass effect and destruction of the left temporal bone extending into the scalp , suggesting the possibility of meningioma .
no evidence of calcification was noted within the lesion preoperative mri of the brain showed a left temporal lesion , hypointense on t1 , heterointense on t2 , with heterogenous enhancement the patient underwent left temporoparietal craniotomy and decompression of the lesion .
the operative findings suggested that the lesion was extradural , with erosion of bone in some areas and involvement of the overlying temporalis muscle .
the histopathological examination showed round - to - oval cells arranged in lobules , separated by a thin vascular channel , having vesicular nuclei , with indistinct nucleoli .
it was negative for cd20 , cd3 , myosin , and glial fibrillary acidic protein .
the overall features were compatible with a primitive neuroectodermal tumor ( pnet ) , with a possibility of ewing 's sarcoma in the temporal region .
the tumor was positive for t ( 11 ; 22 ) ( q24 ; q12 ) translocation detected by fluorescent in situ hybridization ( fish ) in the tumor biopsy sample .
the findings of further metastatic workups , including ct scans of the thorax and abdomen and a bone scan with technetium tc-99 m , were negative .
ews / pnet 's are characterized by immunoreactivity to the surface antigen cd99 / mic2 , which is expressed in up to 97% of the cases a postoperative ct scan of the brain revealed a large extradural and subdural hematoma in the left frontotemporal region , with a postoperative craniotomy defect and scalp edema .
the child went on to receive 12 weeks of chemotherapy with vincristine , doxorubicin , and cyclophosphamide , alternated with ifosfamide and etoposide .
the treatment was completed with the same combination of chemotherapeutic drugs for another 24 weeks .
james ewing ( 18661943 ) first described the tumor , establishing that the disease was different from lymphoma and other types of cancer known at that time . in 1921 , he described a lethal primary bone lesion that affects children and young adults and most frequently originates in the long bones ( 47% ) , pelvis ( 19% ) or ribs ( 12% ) .
the skull is rarely involved , probably in less than 4% of the cases , with the frontal and parietal bones being the most commonly affected .
extraosseous ewing 's sarcoma ( ees ) has been recognized as a distinct disease entity that afflicts young adults in the second and third decades of life , with equal sex predilection .
the ees commonly involves the paravertebral regions of the spine and in rare instances , these lesions arise in the intracranial compartment , where they have been commonly misdiagnosed as c - pnet , because of the similarity in their histological appearance .
very few cases of the central nervous system extraosseous ewing 's sarcoma ( cns - ees ) have been reported in pathology literature.[611 ] jay et al .
was probably the first to describe a patient with an isolated posterior fossa mass that histologically resembled a medulloblastoma , but demonstrated the t(11;22 ) ( q24;q12 ) translocation , which confirmed cns - ees .
as far as our knowledge goes , this is the seventh case we are reporting .
the differential diagnosis of an intracranial round cell tumor is primitive neuroectodermal tumor ( neuroblastoma ) , lymphoma , rhabdomyosarcoma , and ewing 's sarcoma .
the histological examination reveals that these tumors are composed of small , undifferentiated neuroectodermal cells and frequently demonstrate immunohistochemical and/or electron microscopic features of glial or neuronal differentiation .
recent advances in the molecular classification has allowed a clear pathological distinction between c - pnet and cns - ees .
cns - ees is known to demonstrate in 97% of the patients , a strong membrane expression of the mic-2 gene product , designated cd99 , which is specifically recognized by the monoclonal antibodies o13 and hba71.[1316 ] in addition , the chromosomal translocation t(11 , 22)(q24;q12 ) , detected by fish , is found in more than 90% of ees .
this nonrandom translocation is not found in the central primitive neuroectodermal tumors ( c - pnet ) such as the medulloblastoma and supratentorial pnet .
although , cns - ees is histologically similar to c - pnets such as the medulloblastoma , it differs significantly in clinical behavior , treatment , and prognosis .
the treatment options available for patients with cns - ees are similar to those of ees elsewhere in the body and include multimodality treatment comprising of surgery , chemotherapy , and radiation .
patients with c - pnet also require surgery ; however , the chemotherapeutic and radiation therapy protocols differ from those used for cns - ees .
multiagent chemotherapy regimens including cyclophosphamide , ifosfamide , doxorubicin , dactinomycin , and etoposide have been shown to be effective in localized ewing 's sarcoma , in various trials .
the primary treatment for localized ess consists of neoadjuvant chemotherapy , with a combination of vincristine , doxorubicin , and cyclophosphamide , alternating with ifosfamide and etoposide , given for 12 to 24 weeks , followed by definitive local treatment of surgery or radiation , or surgery and postoperative radiation directed at the primary site .
the treatment is completed with administering chemotherapy with a similar combination for a total of 36 to 49 weeks .
because of the small number of patients , the prognosis of cns - ees is not clearly known , although it has been suggested that patients with ees that arises from structures within or around the cns may have a more favorable outcome than patients with c - pnet .
 ewing 's sarcoma / peripheral primitive neuroectodermal tumors occur most often in bone and soft tissues of children and young adults . 
 the intracranial manifestation of the disease is rare , and when present , this is often misdiagnosed with other varieties of primary brain tumors . 
 we report such a case of extraosseous ewing 's sarcoma , which was initially suspected to be a case of meningioma in an 11-year - old girl . 
INTRODUCTION
CASE REPORT
DISCUSSION