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 a bewildering variety of moles. The easiest way to classify moles is by the location of the melanocytic nests. Only a pathologist can say for sure where the nests of melanocytes are located. Thankfully, however, you do get a pretty idea of the mole sub-type by just looking at it.
- 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).
Congenital Moles are present at birth or early childhood. These tend to become raised and roughened with age, much like a dermal nevus.
Other common types of mole are Blue nevus, Atypical Mole (Dysplastic Nevus), Halo Nevus, & recurrent nevus. The list goes on … 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).