Neoplasms with histology and immunohistochemistry similar to gastrointestinal stromal tumors may occur primarily outside the gastrointestinal tract, usually in the omentum and mesentery. These are referred to as extragastrointestinal stromal tumors (EGISTs). Retroperitoneum is a very rare site for such neoplasms. We report a patient with EGIST in the retroperitoneum, elaborating the cross-sectional imaging and histopathologic findings.

Neoplasms in the region of filum terminale are not uncommon. Myxopapillary ependymoma is the commonest tumor at this location. The differentials reported for this entity are nerve sheath tumor, meningioma, paraganglioma, intradural metastases, lymphoma, other varieties of ependymoma, subependymoma, astrocytoma, ganglioglioma, hemangioblastoma, and primitive neuroectodermal tumor (PNET). PNET may very rarely present as an intradural thoracolumbar mass. We present pre- and post-therapy magnetic resonance imaging (MRI) features of a patient with proven primary spinal primitive neuroectodermal tumor (PSPNET) of peripheral subtype.