Dermal melanocytosis of the scalp associated to intracranial melanoma: malignant blue nevus, neurocutaneous melanosis, or neurocristic cutaneous hamartoma?

Intracranial invasion of cellular blue nevus is extremely rare, and its malignant transformation is even less common. The differential diagnosis includes neurocutaneous melanosis and neurocristic cutaneous hamartoma. A 50-year-old female presented with intracranial melanoma in contiguity with a congenital blue nevus on the scalp. The patient showed a wide pigmented lesion on the scalp that had grown in the last few years over the congenital blue nevus. Magnetic resonance imaging revealed an intracranial tumor lying contiguous to the nevus. Despite aggressive surgery, the tumor relapsed and the patient developed systemic metastases. We report a rare case of cellular blue nevus showing an unexpected aggressive behavior with extensive extra- and intracranial expansion and distant metastases.