Solitary Epicranial Neurofibroma with Neurofibromatosis Type 1-Related Germline Mutation: Case Report

A 33-year-old male became aware of a painless soft mass in the left occipital region. His medical and family history were unremarkable for neurofibromatosis type 1 (NF1) or other genetic disorders. Physical examination showed no signs of NF1. Neurological and ophthalmological examinations found no abnormality. Cranial computed tomography showed an isodense mass located subcutaneously with irregular deformities in the adjacent occipital bone. Magnetic resonance (MR) imaging demonstrated that the lesion, 7.5 × 5.5 cm in diameter, was hypointense both on T₁- and T₂-weighted images and intensely enhanced after gadolinium infusion. The patient requested to remove the large mass. The subcutaneous tumor was well circumscribed, encapsulated, and less vascular, and resected en bloc. The histological diagnosis was neurofibroma without findings of cell atypia, whereas genomic exploration identified abnormal gains in NF1 gene, and resultant absence of neurofibromin, a protein coded on NF1 gene. Solitary neurofibromas in “clinically” non-NF1 patients may originate from the genomic changes in NF1 gene.