[A 33 year old woman with a six-year history of slight thoracic-abdominal pain]. / Mujer de 33 años de edad con leve dolor toracoabdominal derecho de seis años de evolución, súbitamente agudizado.

We present a case of a benign hybrid nerve sheath tumor showing features of both cellular schwannoma and perineurioma.The patient was a 33 year-old female who presented with a 6 month history of pain in the thorax-lumbar region.Axial CT and MIR images showed and homogeneously enhancing solid oval mass involving the left paravertebra region in contact with the vertebral foramina T9-T11. Morphologically the tumor presented a well formed capsule and showed a uniform highly spindle cell proliferation. The spindle cells were arranged in whorls and intersecting fascicles with focal intervening sclerosis and relatively uniform cellularity with a prominent perivascular lymphocytic infiltrate. No cytological atypia, necrosis or mitoses were present. A second cell component was present composed of spindle-shaped cells with inconspicuous bipolar, pale, eosinophilic cytoplasm with oval nuclei. By immunohistochemistry there was a diffuse staining for S-100, and the elongated bipolar cells were EMA, Glut-1 and Claudin-1. To our knowledge this is the first reported case of a hybrid cellular schwannoma/perineurioma.