Oncocytic Melanoma: A Study of a Rare Entity.

The authors report the second case of oncocytic melanoma, one of the rarest known melanoma variants. The diagnosis was established by Fontana stain positivity, expression of S100 protein as well as gp100/HMB45, and demonstration of numerous mitochondria by ultrastructure. Because it is known that some oncocytic tumors of the thyroid gland and kidney contain point mutations and common deletions of mitochondrial DNA, the complete mitochondrial DNA of the reported oncocytic melanoma was also studied. It was normal except for 2 private separate point mutations, predicted to be not pathogenic, which do not seem to play any role in the tumor phenotype.