A Rare Case of Aggressive Melanotic Schwannoma Occurred in Spinal Nerve of a 59 Year Old Male Malignant melanotic nerve sheath tumors in the spinal canal of psammomatous and non psammomatous type: Two case reports Non psammomatous melanocytic schwannoma presenting as a subcutaneous nodule: A rare presentation of a rare lesion Interosseous Malignant Melanotic Nerve Sheath Tumor of the Sacrum Treated With an Innovative Reconstruction Technique Cureus