Primary Extraosseous Ewing Sarcoma of the Thoracic Spine Presenting as Chest Pain Mimicking Spinal Schwannoma

Background: Extraosseous Ewing sarcoma (EES) usually has a pseudocapsule and high vascularity, making it well circumscribed and focally dense with contrast enhancement on magnetic resonance imaging (MRI). Consequently, it is difficult to diagnose and distinguish from other spinal tumors, based on pretreatment radiologic findings alone. Here, we present a case of EES involving the thoracic spinal column, which was suspected to be spinal schwannoma through pretreatment radiologic findings.

Case description: A 54-year-old woman was admitted to our hospital with upper back and left-sided chest pain. Contrast-enhanced MRI of the thoracolumbar spine showed a 17- × 12-mm-sized mass in the epidural region and left neural foramen at the T6-7 level. Our preliminary diagnosis was spinal schwannoma. The patient underwent T6 hemilaminectomy. Intraoperatively, the lesion appeared as gray-colored soft mass with high vascularity, which seemed to have originated from the left T6 nerve root. The tumor was excised with en bloc resection. Histopathologic examination of the lesion revealed classical Ewing sarcoma with high cellularity of small round cells. Immunohistochemistry revealed strong positivity for cluster of differentiation 99 and FLI-1. Intensity-modulated radiation therapy was performed. The patient did not receive chemotherapy. Five years after surgery, follow-up spinal MRI and positron emission tomography computed tomography scan revealed no recurrence of the tumor or new lesions.

Conclusions: Clinicians should consider EES in the differential diagnosis of other neural foraminal spinal tumors, such as schwannoma. If clinicians are confident that EES has been removed completely and there are no other lesions, radiotherapy is sufficient and additional chemotherapy may not be necessary.

Keywords: Extraosseous Ewing sarcoma; Pseudocapsule; Schwannoma; Spine; Surgery.