Dermal melanocytosis. Report of an unusual case.

A 32-year-old Portugese woman presented with a bluish spot on the right hand. It had appeared at the age of 11 years. The histologic examination revealed typical dermal melanocytes. Although clinically this lesion was typical of an aberrant and persistent Mongolian spot, it exhibited, both histologically and ultrastructurally, also some features of the common blue nevus. Dermal melanocytosis of the macular type, as observed in our patient, is very rare.