Malignant melanoma showing ganglioneuroblastic differentiation - Report ofa unique case

We report a case of metastatic malignant melanoma in an inguinal lymph node , expressing ganglioneuroblastic differentiation. This was characterized by the presence of discrete nests and islands of large ganglion cells with ab undant cytoplasm and eccentric nuclei with prominent nucleoli admired with smaller primitive neuroblasts. The cells were separated by pale pink fibril lar material representing neuritic cell processes. These foci of ganglioneu roblastoma were seen over a background of an otherwise typical metastatic e pithelioid, focally melanotic, malignant melanoma. Immunohistochemistry sho wed positivity for neurofilament, synaptophysin, chromogranin, vasoactive i ntestinal peptide, and glial fibrillary acidic protein in the areas with ga nglioneuroblastic differentiation, but not in the melanocytic component. Co nversely, HMB45 positivity was expressed by the melanocytic cells only. S-1 00 protein and Melan-A, a putative melanocytic marker, showed positivity in both melanocytic and ganglioneuroblastic components. Ultrastructurally, ne uritic cell processes and dense core neurosecretory granules were identifie d in the ganglionic and neuroblastic cells. A subsequent nodal metastasis i n the same region showed focal neuroblastic differentiation without the gan glionic element. No evidence of neuronal or ganglionic differentiation was seen in the primary skin melanoma.