Summary

Malignant Triton tumor is a rare variant of peripheral nerve sheath tumor with rhabdomyoblastic differentiation. Histologically it is a biphasic tumor consisting of spindle cells with wavy nuclei and eosinophylic round cells with pleomorphic nuclei. Both components are neoplastic. Immunohistochemically S-100 protein positivity confirms the Schwann cell origin of the spindle cell component, while desmin positivity helps to prove the rhabdomyoblastic differentiation in the round cell component. In this study we present a 58 year old male patient with a malignant Triton tumor of the L3 vertebral nerve root which showed two recurrences six and sixteen months after the diagnosis. The patient died after 16 months of follow-up. The prognosis of the malignant Triton tumor is worse than the other malignant peripheral nerve sheath tumors and although rare, should be considered in the differential diagnosis.