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ewing 's sarcoma ( ews ) accounts for 10% of malignant bone tumors and commonly arises from the long bones , pelvis , and ribs .
primary ews arising from cranial bones is rare and accounts for only 1%4% of all ews .
we report the case of a 15-year - old girl with ews of the skull and discuss the treatment of this rare entity .
a 15-year - old girl presented with swelling on the vertex of the head since 1 year , rapidly enlarging since few days . computed tomogram ( ct ) showed an expansile lytic lesion with elevation of periosteum in the mid frontoparietal calvarium projecting into the scalp with heterogenous soft - tissue component [ figure 1 ] .
the lesion was extending intracranially . a magnetic resonance ( mr ) angiogram showed lytic destructive mass lesion of frontal calvarium breaching the dural lining and partially encasing the superior sagittal sinus [ figure 2 ] .
histopathological examination showed a highly cellular and vascular tumor composed of uniform round cells with scanty cytoplasm and round vesicular nucleus with periodic acid 
on immunohistochemistry , the cells showed strong membrane positivity for mic 2 and were negative for leukocyte common antigen ( lca ) and synaptophysin [ figure 4 ] .
the picture was suggestive of ews . computed tomography scan showing the expansile lytic lesion in frontoparietal calvarium projecting into the scalp with soft - tissue component magnetic resonance angiogram showing the destructive mass lesion in frontoparietal calvarium section showing cellular small round cell tumor with vesicular nuclei and vacuolated cytoplasm .
a mitotic figure is seen toward the center of the field ( h and e , 400 ) tumor cells showing diffuse and strong membrane staining for mic 2 ( 200 ) her hematology and serum chemistries were normal .
a cerebrospinal fluid study , ct of the chest and bone marrow examination were normal .
she received combination chemotherapy with vincristine , doxorubicin , cyclophosphamide alternating with ifosfamide , and vp16 for 1 year .
ews is a highly malignant bone tumor seen in children and young adults , and primary involvement of the skull is rare .
ews of the skull affects the frontal , parietal , and temporal bones and sometimes the skull base .
ews typically grows extradurally and often reaches a large size before it is clinically detectable . in a retrospective study , among 332 cases of ews ,
about 90% of the cases occur in the first two decades of life , peak incidence is between 5 and 13 years of age , and males are affected more frequently .
the most common symptoms are headache and scalp swelling , the duration of which ranges from 2 weeks to 2 years .
plain x - ray of the skull shows a lytic lesion with mottling and erosion , and the classical onion peel appearance is rare .
ct and mr imaging are useful to understand the size , extent , and involvement of dura and brain parenchyma .
ct scan is useful to delineate bone involvement , and on mri , the mass is hypo- to iso - intense on t1-weighted and iso- or hyper - intense on t2-weighted with heterogeneous enhancement on contrast . on bone scintigraphy
histologically , these tumors are characterized by sheets of small round blue cells with a high nuclear - cytoplasmic ratio .
immunohistochemistry helps differentiate ews from other small round cell tumors such as rhabdomyosarcoma , neuroblastoma , and lymphoma .
ews is positive for cd99 and vimentin and negative for desmin , lca , and synaptophysin .
ews is characterized by a balanced translocation between chromosome 11 and 22 which fuses ews gene on chromosome 22q12 with fli1 gene on 11q24 . rarely , translocation t(21;22 ) or t(7;22 ) is observed .
fli1 fusion transcript type 1 being associated with improved outcome compared with that in patients with other fusion transcript types .
the incidence of metastasis is less , radiologically the typical onion peel appearance may not be seen , and the prognosis is better than the disease in other sites . like extracranial ews , multimodal therapy is the treatment of choice for cranial ews also .
surgical resection is crucial in the management of ews of the skull and is the preferred approach if the lesion is resectable .
a radical excision should be attempted to minimize the tumor mass . in calvarial ews , as majority of patients present with rapidly enlarging lesion and raised intracranial pressure , upfront surgical resection and decompression become imperative unlike ews of extremities where presurgical chemotherapy is used to shrink the tumor . in calvarial
ews , it is usually not possible to get a margin free of microscopic disease and hence local radiotherapy is recommended at a dose of 4050 gy .
current chemotherapy regimen consisting of a combination of vincristine , cyclophosphamide , doxorubicin alternating with ifosfamide , and etoposide used for the treatment of ews has given a 5-year survival rate of about 70% .
with total excision , radiation , and standard chemotherapy , the 5-year survival ranges from 39% to 65% .
primary ewing 's sarcoma ( ews ) arising from cranial bones is rare and accounts for only 1%4% of all ews . 
 we report the case of a 15-year - old girl with ews of the frontoparietal region of the skull . 
 she underwent excision following which she received combination chemotherapy with vincristine , doxorubicin , cyclophosphamide alternating with ifosfamide , and vp16 and local radiation of 45 gy . 
 she is alive in complete remission at 40 months .