An unusual primitive neuroectodermal tumor in the thoracic epidural space

Abstract

Primitive neuroectodermal tumor (PNET) is a generic term used to describe a group of histologically indistinguishable neoplasms, including cerebellar medulloblastomas, which are located at various sites in the central nervous system. Primary epidural PNETs are rare and few patients have been reported. We report a 15-year-old girl who presented with gradual onset, over 1 month, of upper back pain and bilateral lower leg weakness. A thoracic spine MRI showed a dumbbell-shaped epidural mass at T2-4 with right paraspinal and posterior mediastinal extension. Surgical resection of the epidural tumor for decompression was performed. The pathologic examination revealed a PNET. Primary spinal PNETs typically have a poor prognosis and optimal therapy has not yet been defined. Surgical resection, with the combination of chemo-radiotherapy or radiotherapy, leads to better outcomes. However, primary epidural PNETs may be classified as a subtype of spinal PNETs because they are free from intrathecal invasion. For these patients, surgery alone and surgery combined with radiotherapy or chemo-radiotherapy remain controversial. Our patient received surgery alone and, 1y ear later, has experienced no local recurrence within the epidural space but the mediastinal part of the tumor has enlarged.