An Autopsy Case of Neurofibromatosis Type 1 Mutation Detected in a Duodenal Lesion of Malignant Melanoma: A Case Report

We report an autopsy case of duodenal malignant melanoma (MM) in a patient with neurofibromatosis type 1 (NF1). The patient had an anamnesis of choroidal MM, and the duodenal lesion was initially suspected to be a metastasis from the choroidal tumor. At autopsy, the duodenum was occupied by a tumor composed of large atypical cells on histopathological examination. Immunohistochemically, the nuclei of large atypical cells were positive for Melan A, HMB-45, and SOX-10, confirming the diagnosis of MM. Next-generation sequencing (NGS) of the duodenal tumor sample identified an NF1 mutation, with no other gene mutations clearly associated with malignant transformation.