Skull Base Primary Ewing Sarcoma: A Radiological Experience of a Rare Disease in an Atypical Location.

BACKGROUND Ewing sarcoma and primitive neuroectodermal tumor are rare tumors grouped under the spectrum of the Ewing sarcoma family of tumors. These highly malignant tumors involve the bones and commonly occur in children. Ewing sarcoma of the skull bone accounts for only 1% of all Ewing sarcomas, with primary skull base Ewing sarcoma occurring in less than 1% of cases. We present a case of skull base Ewing sarcoma with complete symptom recovery and near-total radiological resolution. CASE REPORT A 4-year-old girl initially presented with a 2-month history of vomiting, poor oral intake, weight loss, and gradual visual deterioration followed by acute symptoms of fever, breathing difficulties, and seizure. Initial computed tomography and magnetic resonance imaging of the brain displayed a large sinonasal mass with extensive regional infiltration and bony destruction and no evidence of distant metastasis. A transnasal biopsy was taken. The histopathology result revealed features of skull base Ewing sarcoma. The child was given a combination of radiotherapy and chemotherapy, to which she responded well, with a minimal residual tumor. CONCLUSIONS Skull base Ewing sarcoma is a rare entity, presenting a challenge to the reporting radiologists. Differential diagnoses of esthesioneuroblastoma, olfactory neuroepithelioma, and, more commonly, sinonasal carcinoma can be misleading since they have similar radiological appearances to skull base Ewing sarcoma, which differs in treatment regimen and prognosis. Therefore, a combination of histopathological appearance, radiographic findings, and clinical correlation is important to determine the correct diagnosis, establish the appropriate treatment regime, and improve the patient's survival.