Primary Unilateral Ethmoidal Ewing Sarcoma With Orbital Extension: A Report of a Rare Case

Ewing Sarcoma (EWS) is a rare, aggressive, small round blue cell tumor that predominantly arises in children and young adults. Sinonasal localization is a rare and difficult presentation to diagnose due to nonspecific clinical and histopathological features.  A 21-year-old male patient presented with acute left-sided epistaxis associated with periorbital swelling and epiphora. Contrast-enhanced CT revealed a well-defined lobulated heterogeneously enhancing iso-hyperdense lesion in the left ethmoid sinus with extensions and mass effect. Histopathological examination demonstrated features of a small round blue cell tumor. Immunohistochemistry showed diffuse nuclear positivity for NKX2.2 and focal membranous positivity for CD99, with negative staining for pan-cytokeratin, CD45, chromogranin, and synaptophysin, confirming the diagnosis of EWS. The patient was counseled regarding multimodal treatment options, including surgery, chemotherapy, and radiotherapy. However, he declined treatment and was discharged against medical advice, and was subsequently lost to follow-up. Sinonasal EWS is a rare entity with overlapping histomorphological features that complicate the diagnosis. A systematic approach incorporating histopathology and immunohistochemistry is essential for accurate identification. This case highlights an extremely rare unilateral ethmoid sinus presentation of sinonasal EWS and underscores the importance of considering it in the differential diagnosis of sinonasal masses in young adults.