Malignant melanotic nerve sheath tumor 2026-03-09T07:51:16Z Malignant melanotic nerve sheath tumors (MMNSTs) are uncommon pigmented tumors of Schwann cell origin, most often found along the spinal nerves. MMNSTs were formerly known as melanotic schwannoma. Although MMNSTs can occur along cranial nerves, they tend to grow along the dorsal spinal nerve roots, and patients often present with indolent pain, weakness, or paresthesia along a corresponding dermatome. On imaging, spinal MMNSTs generally appear similar to the appearance presented in the current case: intradural, extramedullary tumors. In the spine, the tumors typically grow along spinal nerve roots, sometimes assuming a dumbbell configuration if they extend through a foramen. Tumors demonstrate enhancement on CT and are FDG-avid on PET. MMNST often carry an inactivating mutation in the protein kinase A inhibitory subunit gene protein kinase cAMP-dependent type I regulatory subunit alpha (PRKAR1A) on chromosome 17p22-24, which acts as a tumor suppressor. MMNST occur in some patients with Carney Complex. Soft tissue sarcoma