Interosseous Malignant Melanotic Nerve Sheath Tumor of the Sacrum Treated With an Innovative Reconstruction Technique.

Intraosseous malignant melanotic nerve sheath tumors are extremely uncommon peripheral nerve sheath tumors that typically present with benign clinical and histopathological features but with more aggressive long-term behavior. These tumors commonly originate from the dorsal nerve roots, sympathetic chain, cranial nerves, and lumbar plexus but may be found throughout the body. It usually presents with gradual compressive symptoms over months to years, like the typical presentation of schwannomas. The mainstay of treatment is surgical resection, with gross total resection recommended. Additional treatment with adjuvant therapy for recidivist or metastatic disease is less well-defined due to the rarity of these tumors. Adjuvant radiation following resection that is not gross total or that accomplishes clear surgical margins is advocated by some authors, although there is no strong evidence for it in the literature. In this report, we describe an extremely rare case of gradual onset, progressive spinal cord dysfunction in a patient with a lumbosacral intraspinal malignant melanotic nerve sheath tumor with bony invasion that was treated with an innovative reconstruction technique that to the best of our knowledge is first described in our paper. The patient achieved excellent functional and neurological outcomes after the surgical excision and reconstruction.