Moles are the most common of the benign lesions.
What are the clinical features?
A mole is simply an accumulation of melanocytes, the pigment-forming cells of the epidermis (outer layer of skin). These nests of melanocytes come in a bewildering variety, and the easiest way to classify them is by the position of the nests within the skin. The nests can be superficial, deep, or a mixture of the two and include:
- Junctional Nevus nests which occur at the junction between the epidermis and dermis and are usually flat and brown.
- Dermal Nevus occur in the dermis, which is a lower level of the skin and can be raised, pink, skin coloured or brown. This type of mole often has hairs growing from it. Dermal nevi moles on the face are called Miescher Nevus, and on the body, they’re called Unna Nevus.
- Compound Nevus are as their names suggest, a combination of the previous two types of moles and occur between and in the epidermis and dermis.
A mole can be identified as Junctional, Dermal or Compound by its dermoscopic appearance and a biopsy would confirm the diagnosis. Ultimately, what matters is that the mole is not melanoma!
There are several different types of moles, including:
- Congenital moles are present at birth or early childhood and become raised and roughened with age, much like a dermal nevus.
- Blue nevus are dark blue or nearly black in colour.
- Atypical Mole, also called Dysplastic Nevus and can look very much like melanoma.
- Halo Nevus has a ‘halo’ around it, suggesting that the immune system is ‘getting rid of it.’
- Recurrent nevus are previously cut out moles that have reappeared, such as after a shave biopsy.
- Speckled Lentiginous Nevus are typically large, flat and speckled in appearance.
- Spitz nevus, a dangerous mole that typically requires a biopsy to eliminate the possibility of melanoma.
- Labial Melanotic Nevus, a benign mole on the lip.
What do the different types of Moles look like?
Flat Moles (Junctional Nevi)
Thick moles (Dermal Nevi)
This type of mole combines the two types mentioned above (Junctional moles and Dermal moles). They usually appear raised and dark and can have features similar to melanoma.
Congenital nevi moles usually appear at birth or in infancy.
Acral Moles (on the palms or soles)
Other types of mole
Speckled nevus moles present exactly as their name suggests and recurrent nevis moles which have regrown after an incomplete removal.
Why Do Moles Matter?
Facts about Moles and Melanoma
If everyone has moles, then you might wonder why they matter. While it’s true that most moles are harmless, here are some less benign facts about them:
- Moles change in appearance with age – and can develop into melanoma.
- The greater the number of moles, the greater the risk of melanoma, especially if you have more than 100 moles.
- Melanoma can develop from a simple, benign mole – but it’s more common for a melanoma to develop spontaneously.
- Moles usually grow in childhood and early adulthood, and if you see a new mole on your skin when you’re over 40 it could be a melanoma.
- Some people have so many moles that they need a comprehensive skin check to find dangerous ones.
- A melanoma starts out looking like a mole and can be tiny.
- Moles usually start flat and become thicker and darker with age – leading to concerns about melanoma and cosmetic concerns.
Melanoma may develop from a mole – although it’s more common for a melanoma to develop spontaneously.
After an excision and biopsy of a mole, you’ll get a Pathology Report detailing the results. A nevus is only removed for either cosmetic concerns or to exclude a melanoma (or another type of skin cancer).
In a junctional nevus, the nests are located along the base of the epidermis.
The melanocyte nests are found both in the lower layer of the epidermis (as for a junctional nevus) and also the dermis (as for a dermal nevus) – it’s basically a combination of junctional & dermal.
The nests of melanocytes are found in the dermis ie. in the deeper layer of skin than with a junctional nevus.
Dysplasia is an important term in pathology reports. Dysplastic melanocytes look abnormal in some way.
The cells may have a nucleus that’s abnormal in shape and colour. The nuclei may be angulated, a darker colour (hyperchromasia), or it may nucleoli may be prominent. There may also be bridges between epidermal projections, which are finger-like projections into the epidermis from the layer below, or even some fibrosis (scar-like tissue).
If the pathologist can’t tell a lesion from a melanoma, then it’s called a severely dysplastic nevus.