Birthmarks are marks on the skin at birth or shortly afterwards. One of the two major types of birthmarks is the pigmented birthmark (the other, vascular birthmark). Pigmented birthmarks are those that are associated with a localized overgrowth of melanocytes. They include melanocytic nevus (mole), café au lait spots, and Mongolian spots.
A melanocytic nevus is a pigmented birthmark (i.e. black, brown, or tan in color). It may be flat or raised. It may also have hair growing out of it. It contains mainly of nevus cells. A nevus cell is a form of melanocyte that is larger in size, with more cytoplasm, and lacks dendrites. Nevus cells in the skin may be found particularly at the dermoepidermal junction or in the dermis.
Melanocytic nevus may be congenital or acquired. Congenital melanocytic nevus is already present at birth and will persist throughout life. This type of nevi has a higher risk of developing into melanoma (skin cancer) later in life than an acquired nevus has.
- nevocytic nevus
- nevus-cell nevus