Tohoku J. Exp. Med., 2006, 209(4)

Ewing's Sarcoma in the Spinal Nerve Root: A Case Report and Review of the Literature

SHUJI ISEFUKU, MASAHIRO SEKI, TAKAHIRO TAJINO,¹ MICHIYUKI HAKOZAKI,¹ SHIGEYUKI ASANO,² HIROSHI HOJO³ and MASAHITO HATORI⁴

Department of Orthopedic Surgery, Iwaki Kyouritsu General Hospital, Iwaki, Japan, ¹Department of Orthopedic Surgery, Fukushima Medical University, Fukushima, Japan, ²Department of Pathology, Iwaki Kyouritsu General Hospital, Iwaki, Japan, ³Department of First Pathology, Fukushima Medical University, Fukushima, Japan, and ⁴Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan

Ewing's sarcoma (ES) is a highly malignant tumor composed of uniform small round cells. Recently, a single biologic entity, Ewing's sarcoma family of tumors (ESFT) has been accepted. The entity includes ES, extraskeletal Ewing's sarcoma (EES) and primitive neuroectodermal tumor (PNET). ESFT cells have immunoreactivity for CD99, an antigen determined by the MIC2 gene. Most ESFT has the (11;22) (q24;q12) translocation. The translocation results in the fusion of the EWS gene with the transcription factor gene FLI1 which has been considered a hallmark of ESFT. We present an extremely unusual case with ESFT in a spinal nerve root mimicking a neurogenic dumbbell tumor. A male aged 20 years noticed pain in his right buttock. Magnetic resonance imaging (MRI) revealed a mass in the right L5/S intervertebral foramen and the lesions in the sacrum. Surgery was performed with a presumptive diagnosis of a nerve sheath tumor. At surgery, the tumor was located in the right L5 nerve root sleeve. The sacral lesions were observed closely. At one month after surgery, radiologically multiple lesions were detected in the pelvic bones. Microscopically the lesions from the root and ilium were composed of small round cells immunoreactive for CD99. Reverse transcription-polymerase chain reaction detected transcripts resulting from the fusion of the EWS gene with FLI1 genes in the iliac lesion. Immunoreactivity for CD99 and detection of the EWS-FLI1 hybrid transcripts are important for the correct diagnosis of ESFT arising in an unusual location.

keywords —— Ewing's sarcoma; Ewing's sarcoma family of tumors; extraskeletal Ewing's sarcoma (EES); primitive neuroectodermal tumor (PNET); nerve root

© 2006 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2006, 209, 369-377

Correspondence: Masahito Hatori, M.D., Ph.D., Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryomachi, Aoba-ku, Sendai 980-8574, Japan.

e-mail: mhato@mail.tains.tohoku.ac.jp