A congenital pigmented or melanocytic nevus is a dark-colored, often hairy patch of skin that is present at birth.
Giant hairy nevus of the hand, dorsal aspect (image source)
The congenital melanocytic nevus (plural, nevi) presents as a circumscribed, light brown to black patch or plaque, potentially very heterogeneous in consistency, covering any size surface area and any part of the body. The appearance of the congenital melanocytic nevus is similar to those of nevi acquired after birth. However, congenital ones are usually larger in diameter and may have excess terminal hair, a condition called hypertrichosis. If over 40 cm projected adult diameter with hypertrichosis, it is sometimes called giant hairy nevus; more usually these largest forms are known as large or giant congenital melanocytic nevus. The estimated prevalence for the largest forms is 0.002% of births . (from wikipedia)Other similar posts