How do Moles Form?
What Is a Mole?
A mole (also known as a naevus or nevus) is a common skin growth made up of a cluster of pigment-producing cells called melanocytes. These cells are responsible for producing melanin, the pigment that gives skin its colour.
Most moles are harmless. They can appear anywhere on the body and may be flat or raised, smooth or slightly rough, and range in colour from light brown to dark brown, black, pink or even skin-coloured.
How Do Moles Form?
In summary, moles form when melanocytes grow in groups rather than spreading evenly across the skin.
In normal skin, melanocytes are distributed throughout the top layers of the skin, creating an even skin tone. When these pigment cells cluster together in one area, they create a visible spot – a mole.
The Science – What Happens at a Cellular Level
Moles form due to a process called melanocytic proliferation. This means that melanocytes – the specialised cells in the skin responsible for pigment production – begin to multiply and cluster together in one localised area, instead of distributing evenly across the skin.
Melanocytes normally sit in the basal layer of the epidermis (the lowest layer of the outer skin). When these cells start to grow in a tight group, they form what is known as a melanocytic naevus (the medical term for a mole).
This clustering can occur in:
- The epidermis (junctional moles – flat, pigmented moles)
- The dermis (dermal moles – raised, skin-coloured or lightly pigmented moles)
- Both layers (compound moles – slightly raised and usually darker)
Why Do Some People Have More Moles Than Others?
The number of moles on your body is mostly determined by your inherited skin type and your early life sun exposure; so people naturally develop more moles due to:
- Genetic makeup
- Fair skin type
- High cumulative sun exposure
- Childhood sunburns
- Living in sunny climates
Lets explore this further
The Role of Genetics in Mole Formation
Genetic mutations play a key role in mole formation. Many moles develop because of acquired mutations in genes that regulate cell growth.
Two of the most important genes involved are:
- BRAF gene – mutations in this gene are found in most acquired (common) moles
- NRAS gene – more commonly linked to congenital moles (those present from birth)
These mutations cause melanocytes to:
- Divide more rapidly
- Avoid normal cell “stop” signals
- Form localised clusters
Importantly, in benign moles, the body activates tumour-suppressor mechanisms that prevent these cells from becoming cancerous. This is why most moles remain harmless.
How UV Radiation Affects Mole Formation
Ultraviolet (UV) radiation plays both a direct and indirect role in mole development.
When your skin is exposed to UV:
- DNA inside skin cells becomes damaged
- Melanocytes increase melanin production as a protective response
- Growth signals are stimulated, encouraging melanocytes to divide
In childhood and adolescence, skin cells are particularly sensitive to UV damage, which explains why childhood sun exposure is strongly linked to mole development later in life.
UV exposure can also cause:
- Darkening of existing moles
- Formation of new moles
- Changes in size or texture
Why Moles Change Over Time
Moles are not static. Their behaviour changes as the skin ages.
This happens because:
- Blood supply to the skin alters with age
- Collagen and elastin in the dermis break down
- Immune surveillance in the skin becomes less effective over time
As a result, moles may:
- Become raised (if cells move deeper into the dermis)
- Lighten or fade
- Develop hairs (due to follicle involvement)
It’s normal for moles to change slowly. Sudden or dramatic changes, however, should always be checked.
How the Body Controls Mole Growth
The body uses built-in safety systems to prevent mole cells from turning cancerous. One of the most important is cellular senescence.
This is a biological “braking system” where cells with growth-promoting mutations are forced into a permanent resting state , stopping them from dividing any further.
This is why:
- Most moles stop growing after reaching a certain size
- The vast majority never become dangerous
When these control systems fail, that is when melanoma can develop – although this is relatively rare compared to the huge number of benign moles people have.
When Should You Be Concerned About a Mole?
While most moles are harmless, it’s important to keep an eye on changes. A mole should be checked by a professional if you notice:
- A change in size, shape or colour
- An irregular or blurred border
- Multiple colours in one mole
- Bleeding, itching or crusting
These changes don’t automatically mean cancer, but they should always be assessed by a qualified clinician.
Never dismiss a hunch that there’s something not quite right. It takes minutes for your GP to check your mole. They may be able to put your mind at rest there and then, but if they share your concern, then they can refer to a specialist for further investigations.
Thankfully most moles turn out to be harmless, but it’s still wise to keep an eye on them in case of any changes.
If you prefer, for peace of mind, cosmetic mole removal at Cosmedics’ Skin Surgery & Laser Clinic can get rid of any unwanted moles quickly and easily with no waiting lists, pain-free treatment and minimal scarring results.
Book a consultation today to get your skin checked by a medical specialist.
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Skin Surgery Laser Clinics
Dr Ross Perry is a qualified and experienced London GP, who founded Cosmedics Skin Clinics in 2003, an independent company specialising in skin treatments such as removal of lesions/blemishes.
Cosmedics’ Skin Surgery Laser Clinic offer private mole removal at a selection of clinics based in London and Bristol. Moles are removed using the latest surgical techniques including laser mole removal; with trained doctors and surgeons.
Our team of qualified and experienced doctors and surgeons also treat other skin blemishes, including sebaceous cysts, skin tags, warts and lipoma using freezing, laser or surgical techniques.
For ultimate peace of mind, Cosmedics Skin Surgery Laser Clinic offer a thorough top to toe mole check carried out by their trained and experienced doctors.
For more information or to book a consultation, please complete the form on this web page or call 020 7386 0464.
