Melanoma associated with congenital intermediate common blue nevus of the scalp - Case report.

Melanomas can arise either de novo (70%) or from pre-existing melanocytic lesions (30%). Of the latter, most cases arise at the dermoepidermal junction from small congenital or acquired non-blue nevi while only a few arise from blue nevi, notably the cellular subtype and less commonly the common (dendritic) type. Melanomas that arise from blue nevi usually occur on the scalp with greater frequency, as in the case described.