Extraskeletal Ewing sarcoma of the buccal space.

Extraskeletal Ewing sarcoma (EES) is a rare soft tissue tumor, and EES of the head and neck is particularly rare. Radiographic imaging of these lesions is crucial given their anatomical complexity and infrequent incidence. Conventional EES imaging features include a large, hyperintense, heterogeneously enhancing lesion, with frequent invasion of local structures. In this case report, a 19-year old male presented with left facial swelling and pain. He underwent sclerotherapy and bleomycin treatment for a presumed lymphatic malformation. Initial imaging demonstrated a rim-enhancing lesion within the left buccal space with no muscle invasion or bony erosion present. Two years later, imaging identified an enlarging buccal mass with destruction of the zygomatic arch and inferolateral orbital wall. The patient underwent surgical resection of the mass. Pathology confirmed the mass to be a small round blue cell tumor and FISH testing confirmed the presence of the EWSR1 gene arrangement that is consistent with EES. The patient tolerated the procedure well and underwent chemoradiation therapy. At three years postoperatively, the patient remains disease free. The presented case demonstrates an unusual presentation of a buccal space EES as a rim-enhancing, centrally hypointense mass with no bony erosion or muscular invasion. The location and atypical imaging appearance of this case offer insight for future diagnosis of EES.