What is a mole?
A mole (nevus or naevus) is a benign “nest” of melanocytes. Looking closely at each mole is a crucial part of a skin cancer check.
Melanocytes are the pigment-forming cells of the lower basal layer of the upper layer of skin (the epidermis). Melanocytes are are normally distributed along the base of the epidermis and make up around 10% of the cells found there. In a mole, the melanocytes are grouped together as “nests” rather than occurring on their own.
There are different types of moles (nevi). The term “simple nevus” refers to these 4 types of mole:
- Junctional Nevus: The nests occur at the junction between the epidermis and dermis. The lesion is flat and brown.
- Dermal Nevus: The nests occur in the dermis (lower down). The lesion is raised and may be pink, skin coloured or brown. Often hairs grow from them. Examples of Dermal nevi are the Miescher Nevus found on the face, and the Unna Nevus found on the body.
- Compound Nevus: a combination of junctional and dermal (the nests occur between the epidermis and dermis, and also in the dermis).
- Small Congential Nevus: present at birth or in early childhood. Congenital nevi tend to become raised with age and have a brown cobblestone.
The other common types of nevi are Blue nevus, Atypical or Dysplastic Nevus, Halo Nevus, & recurrent nevus. Other types of nevi include speckled lentiginous nevus, spitz nevus & labial melanotic nevus.
What do the different types of Moles look like?
The appearance of a mole depends on whether it is junctional (flat & involving only a thin upper layer of skin), dermal (thick & involving deeper layers of skin) or compound (in-between).