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Common Birthmarks - What it is


Nevus sebaceous (NS) are relatively common congenital birthmarks. They consist of increased numbers of sebaceous (oil) glands.

Usually present at birth, NS may be first noted during early childhood.


Epidermal nevi (EN) are relatively common benign congenital birthmarks. They occur as a result of thickening of the top layer of skin (epidermis).

They are usually apparent at birth or become noticeable during early childhood.


Congenital melanocytic nevi (CMN), most commonly known as moles, are very common pigmented birthmarks made up of normal pigment cells. Although usually present at birth, they can also first appear within the first year of life.

CMN are classified according to their greatest diameter in adulthood: Small (<1.5cm), medium (1.5 to 19.9cm), or large (≥20cm).

Common Birthmarks - Symptoms


Nevus sebaceous occurs most commonly on the face and scalp. They appear as solitary or several, yellow to tan, hairless plaques. Lesions may be oval or linear, and can vary in size from a few millimetres to several centimetres. The surface may be smooth, velvety or more warty.

Secondary tumours may occur within NS, most of which are benign. Basal cell carcinoma, a low-grade skin cancer can rarely occur, usually after puberty.

If a new nodule appears in a previously stable NS, your dermatologist may recommend a biopsy to exclude a secondary tumour.


EN appear as tan to brown, velvety or warty plaques, and may be single or multiple. Although most commonly seen on the limbs, they may occur anywhere on the skin. They may occur in a linear or wavy pattern.


CMN appear as flat or slightly raised light to dark brown lesions. Pigment variation and increased hairs may be seen. With time, they can become thicker. Large CMNs may have a rough cobbled-stone surface and more colour variability.

There is a slightly increased risk of cancerous change (malignant melanoma) in all CMN. However, the risk is small in small and medium sized CMN. The risk is higher in large CMN, and can occur earlier.

Large CMN are also associated with increased risk of involvement of the nervous system (brain or spine).

Common Birthmarks - How to prevent?

Common Birthmarks - Causes and Risk Factors

Common Birthmarks - Diagnosis

Common Birthmarks - Treatments


Small NS may be observed, especially in infants and younger children.

Surgical removal may be recommended for larger lesions, those that may lead to significant cosmetic disfigurement or if it interferes with personal grooming (eg. combing of hair), and if there is suspicion of cancerous change.

Nevus sebaceous


EN may be left alone. If treatment is required, treatment options include cryotherapy with liquid nitrogen, dermabrasion, electrosurgery, lasers and surgical removal.

Epidermal nevus


Treatment of CMN depends on the size, site and potential cosmetic effects.

Small and medium sized CMN may be observed. Parents and patients are taught to monitor for changes within the CMN. If there are any concerns, these can be removed by surgery.

Suspicious features that need to be observed for are:
  • A: Asymmetry
  • B: Borders (irregular, blurred)
  • C: Colour (blue, black, red and white)
  • D: Diameter (rapid increase in size)
  • E: Evolution (change over time)

Treatment of large CMN are more complex and require in-depth discussion with your dermatologist, plastic surgeon and paediatrician.

Sun protection is important. Measures include:
  • Avoidance of direct sun between 10.00am to 4.00pm.
  • Use of sunscreens with at least SPF 30 and protection against UVA and UVB.
  • Use of hats, shades and umbrellas when under direct sun.

Large congenital melanocytic nevus

The information above is also available for download in pdf format.

Common Birthmarks - Preparing for surgery

Common Birthmarks - Post-surgery care

Common Birthmarks - Other Information

The information provided is not intended as medical advice. Terms of use. Information provided by SingHealth

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