We describe here a rare case of the transformation of a supratentorial melanocytoma and diffuse melanocytosis into a primary malignant, CNS melanoma. A 71-year-old woman was admitted after suffering from bulbar speech and dysfunction of fine motor skills for three years. Cerebral imaging revealed an inhomogeneous tumor mass in the right frontal lobe. After craniotomy and opening of the dura, a partially black brain surface was exposed. The solid tumor mass was completely resected. Histopathological workup of the surgical specimen (solid tumor) revealed a melanocytoma with transformation into a malignant melanoma. Three months after surgery, an MR scan was carried out, revealing local tumor recurrence and intracranial spreading. At this time the patient agreed to undergo whole brain radiation therapy, which was carried out. At this date patient has survived 18 months since primary diagnosis with progressive neurological symptoms.