Benign peripheral nerve tumor Beacon Health System Pigmented malignant peripheral nerve sheath tumor of the nail unit arising in a patient with neurofibromatosis type I JAAD Case Reports Spotty skin pigmentation and multiple blue naevi as cutaneous markers for spinal melanotic schwannoma BMJ Case Reports A para aortic malignant melanotic nerve sheath tumor mimicking a gastrointestinal stromal tumor: a rare case report and review of literature BMC Surgery Springer Nature Link