Primary Ewing Sarcoma of the Spine Mimicking a Psoas Abscess Secondary to Spinal Infection

Study Design. A case of primary Ewing sarcoma of the lumbar spine is presented. Objective. To present and review a rare case of primary Ewing sarcoma of the lumbar spine that required differentiation from spinal infection. Summary of Background Data. Primary Ewing sarcoma originating from the spinal column is very rare. Because Ewing sarcoma is one of the most aggressive bone tumors with high proliferative and invasive potential, its clinical symptoms and variety of imaging manifestations can mimic the pathologic findings of other diseases, including infectious diseases. Methods. The clinical course, radiologic features, pathology and treatment outcome of a patient with primary Ewing sarcoma of the lumbar spine was documented. Results. The magnetic resonance imaging findings showed an abnormal marrow signal at the L2 vertebra and significant enlargement of the unilateral iliopsoas muscle. Immunologic and molecular analysis of the surgical specimen provided a diagnosis of Ewing sarcoma. Laminotomy followed by multidisciplinary therapy including chemotherapy and radiation therapy was effective for treating this case. Conclusion. We report a case of Ewing sarcoma that mimicked a psoas abscess secondary to spinal infection. Abnormal magnetic resonance imaging images, as well as a confusing clinical course, made diagnosis difficult. When enlargement of the iliopsoas with a vertebral lesion is detected in a child with low back pain, Ewing sarcoma should be included in the differential diagnosis.