Primary Ewing Sarcoma of the Ethmoid Sinus With Intracranial Involvement: A Rare Case and Literature Review.

Ewing sarcoma (ES) is a rare and highly-aggressive tumor. This malignancy derives from primitive neuroectodermal cells. The most frequently-affected population is adolescents and young adults, and the tumor typically grows in the bones. ES of the sinonasal tract is an exceedingly-rare situation. Particularly, primary occurrence in the ethmoid sinus is extremely scarce, with only 27 cases documented worldwide. Extension to the anterior cranial fossa is even thinner on the ground with limited cases in literature. We report the case of a 20-year-old female with history of Hodgkin disease presenting with facial pain, anosmia, and visual impairment on the right side. Imaging revealed a large invasive tumor originating from the right ethmoid sinus, with extension into the orbit and anterior cranial fossa. On biopsy, the tumor showed focal expression of Epithelial membrane antigen (EMA) and CD99 and EWSR1 rearrangement. The diagnosis of ES was confirmed. The patient underwent neoadjuvant chemotherapy with etoposide. Given the stability of the tumor, the patient was deemed inoperable. The decision was to proceed with chemoradiotherapy. Unfortunately, the patient passed away during treatment due to intracranial hypertension with seizures 12 months after diagnosis. This case underscores the rarity of sinonasal ES, particularly with primary involvement in the ethmoid sinus with anterior cranial fossa invasion. We conducted an exhaustive review of literature on similar cases to highlight the importance of a multidisciplinary approach combining advanced imaging, molecular diagnostics, chemotherapy, surgical intervention, and radiotherapy to optimize patients' survival. Sinonasal ES, especially in the ethmoid sinus with cranial extension, is a rare and challenging situation. Detection at an early stage through meticulous imaging, immunohistochemistry, and molecular biology tools is crucial to initiate a multimodal treatment approach. Through this case report and literature review, we aimed to contribute to the growing literature on rare sinonasal malignancies.