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 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 classification is determined by the position of the nests within the skin – superficial, deep, or a mixture of the two. The classification is as follows:
- 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).
The Skin Cancer Doctor can be pretty sure whether the mole is Junctional, Dermal or Compound by its appearance. Many of these diagnoses are presumptive because no biopsy is required. The only way to confirm the diagnosis is to send off the sample to the lab after a biopsy.
Congenital Moles are present at birth or early childhood. These tend to become raised and roughened with age, much like a dermal nevus.
The list of mole types doesn’t stop here! Other common types of mole include:
- Blue nevus: Dark blue, almost black.
- Atypical Mole: Also called Dysplastic Nevus, and may look very much like a melanoma.
- Halo Nevus: Has a ‘halo’ around it suggesting that the immune system is ‘getting rid of it.’
- Recurrent nevus: Moles that have been previously cut-out and come back. Common after a shave biopsy.
- Speckled Lentiginous Nevus: Have a speckled appearance and are usually large and flat.
- Spitz nevus: Usually cause concern enough that a biopsy is required to exclude melanoma.
- Labial Melanotic Nevus: A benign mole on the lip.
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).