What is a congenital nevus?
A congenital nevus is a birthmark that is present at birth or appears within the first months of life. It forms when the pigment-producing cells (melanocytes) gather into a cluster within the skin.
It differs from moles that appear later in two respects: it is present from birth, and it grows along with the child. Proportional enlargement of the mark as the baby grows is an expected finding; on its own, this is not a sign of deterioration.
Congenital nevi are broadly considered in three groups according to their size in adulthood:
- Small — under approximately 1.5 cm in diameter; this is the most common group.
- Medium — approximately 1.5–20 cm.
- Large / giant — exceeding 20 cm; it may involve a region of the body as a whole, and smaller additional moles may be present around it.
Why is removal considered?
Not every congenital mole has to be removed. The decision to operate is made by weighing three considerations together:
- Melanoma risk. The risk rises with size; it is very low in small nevi and appreciably higher in large and giant nevi. Size is therefore the most important determinant of the decision.
- Difficulty of follow-up. In very thick, hairy moles with an irregular surface, it is difficult to detect changes in colour and structure early. Limited monitorability is an argument in favour of removal.
- Appearance and psychosocial impact. Lesions in visible areas such as the face, neck and hands may affect how a child sees themselves, particularly during the school years.
Assessment and follow-up
Where a decision is made to observe a mole, follow-up comprises examination at defined intervals, dermoscopic examination and photographic documentation. So that comparison is possible, it is valuable for photographs to be taken under the same conditions and with a ruler or scale.
Families are asked to report the following changes: rapid growth, a marked change in colour, becoming raised, hardening, itching, bleeding, or a surface that does not heal.
In large nevi located on the head, neck and midline of the back, further imaging may be requested to look for accompanying findings involving the nervous system.
Surgical methods
The aim is to remove the lesion safely while leaving as little scarring behind as possible. The method is chosen according to the size and site of the mole, the age of the child and the elasticity of the adjacent healthy skin.
| Method | How it is performed | When it is suitable |
|---|---|---|
| Excision in a single session | The mole is removed and the skin is closed directly | Small and medium-sized lesions |
| Serial (staged) excision | The lesion is removed piece by piece over several sessions; because the skin relaxes with each session, the next one becomes easier | Lesions that cannot be closed directly but whose surrounding skin is elastic |
| Tissue expander | An expander placed beneath the adjacent healthy skin is inflated gradually to generate extra skin; the lesion is then removed and closed with this skin | Extensive lesions; the method with the best match in colour and texture |
| Skin graft | A thin layer of skin taken from another site is transferred | Very extensive lesions, where adjacent tissue is insufficient |
| Flap reconstruction | Adjacent tissue is moved together with its own blood vessel | Areas such as the face, where matching colour and texture is critical |
In large and giant nevi, treatment is usually a staged programme spread over years; it is not expected to be completed in a single operation.
Timing
Two factors compete in timing: at a young age the skin is highly elastic and the quality of healing is good; on the other hand, each procedure requires general anaesthesia, and because growth continues the result changes over time.
For this reason the plan is made together with the family, in most cases with the start of the child’s school years in mind. Where concern about melanoma is to the fore, timing is determined by that requirement.
What to expect
Surgery leaves a scar; the aim is to make that scar more acceptable than the lesion. In extensive lesions, it is not always possible to eliminate the difference in colour and texture entirely.
Removal also does not wholly remove a person’s overall melanoma risk; skin checks are therefore continued.
Assessment
The right decision in a congenital nevus calls for weighing the risk and the burden of intervention together. For some moles the most appropriate approach is regular observation, for others planned surgery.
If you would like an assessment for a congenital mole in your child, you are welcome to book an appointment; photographs from different periods are valuable for comparison.