ID #138 Extramedullary Intradural Spinal Tumor in Infant with Neurocutaneous Melanosis

Abstract

Neurocutaneous Melanosis (NCM) is a developmental disorder of melanocytic precursors resulting in an exceedingly rare disorder characterized by the presence of melanocytic nevi in the skin and leptomeninges. NCM diagnosis is traditionally made by the presence of large, pigmented congenital nevi in association with meningeal melanosis. The occurrence of intraspinal tumors are rarely reported. We describe the first case of a neonate diagnosed with NCM at birth who was concomitantly found to have a compressive, extramedullary, intradural NCM spinal tumor with leptomeningeal involvement. A full-term infant born at 39 weeks was noted at birth to have a giant melanocytic nevus with innumerable satellite nevi and diagnosed with NCM. MRI showed hyperintense areas on T1-weighted sequences consistent with melanin deposition in the brain and an enhancing mass in the spine from T10-T12 without hydrocephalus. After 3 weeks of life, the patient experienced obstructive hydrocephalus from leptomeningeal dissemination in the pons and upper cervical cord. A palliative VP shunt was placed. At 9 months of age, the patient presented with clinical signs of spinal cord dysfunction including mild axial hypotonia, increased peripheral tone, brisk suprapatellar reflexes, and difficulty bearing weight when lifted in vertical position. A T8-T12 laminoplasty for resection of the extramedullary spinal tumor was performed. Pathology revealed spindle cell neoplasm. At 4-months follow-up, there was no sign of recurrent mass in the spine, but leptomeningeal enhancement around the brain stem and cranial nerves remained. Exome sequencing of the resected tumor revealed two somatic cancer-associated sequence variants of NRAS and RAF1. Although the presence of an activating missense mutation in NRAS supports the diagnosis of NCM and has been previously described in NCM, RAF1 missense mutation is a novel variant identified in this patient. Novel insights from this case may provide important opportunities for targeted therapeutic intervention for infants with NCM.