The suggested work-up for a patient with CMN and a confirmed diagnosis of melanoma is the following: (1) full blood count and lactate dehydrogenase level; (2): CNS MRI with gadolinium contrast, whole-body positron emission tomography–computed tomography scan or computed tomography scans; (3) tissue sample for histopathology, NRAS, and BRAF hotspot genotyping and copy-number analysis (array CGH or SNP array or FISH). The gene discussed is NRAS; the disease is congenital mesoblastic nephroma.