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 Psammomatous melanotic schwannoma a rare neck lump The Annals of The Royal College of Surgeons of England Malignant peripheral nerve sheath tumour (MPNST) Soft tissue sarcoma Cancer Research UK Malignant Peripheral Nerve Sheath Tumors: Latest Concepts in Disease Pathogenesis and Clinical Management Peripheral nerve tumors Symptoms and causes Mayo Clinic Malignant melanotic nerve sheath tumor with PRKAR1A, KMT2C and GNAQ mutations