Congenital Pigmented Naevus

Synonyms: Congenital melanocytic naevus, naevocellular naevus, giant hairy naevus.

These are congenital naevi that are present from birth and initially appear as flat, pigmented lesions of various sizes. They are usually solitary lesions but can be multiple. They may be very large indeed when they are referred to as giant congenital naevi. They are due to a benign proliferation of melanocytes in the dermis, epidermis or both regions.¹ Less commonly they may appear after birth in the first 2 years of life and be histologically indistinguishable from congenital naevi, when they are termed congenital naevus tardive.¹ As the lesion ages it tends to become raised and may sprout hairs.

The major clinical concern with these lesions is the development of malignant melanoma, or anxiety from children or their parents that malignant transformation to melanoma may occur. Congenital naevi are one of many risk factors for the development of melanoma, but melanoma remains a rare diagnosis in younger children, with an incidence of ~0.7 cases per million children in those aged <10 years. However, this incidence has significantly increased by the pubertal years to 13.2 cases per million children in those aged 15–19.¹

• Congenital pigmented naevi are thought to affect 1–2% of newborns internationally.¹
• The rate of malignant transformation is controversial and seems to vary between studies, depending on their populations and methodology.
• Lifetime risk of development of melanoma has been quoted as high as 5–7%.¹
• A recent well-conducted systematic review found an average risk of development of melanoma of 0.7% over 3–24 years in large, prospective studies (statistically the most reliable).²
• The highest risk occurred during childhood and adolescence with median age of 7 years and mean of 15.5 years.²
• The authors calculated a 465-fold increased relative risk of developing melanoma during childhood and adolescence.²
• The risk of developing melanoma was by far highest in congenital melanocytic naevi of ≥40 cm in diameter (those classified as 'garment' naevi).²
• It appears that the actual risk of malignant transformation in lesions of small and moderate size (smaller area than that of the palm) is very low.

• The naevus may be noted at birth, shortly after that, or present medically through parents or adolescent patients later in life.
• Adolescents may present because of cosmetic concerns.
• Concerns about the risk of melanoma, or perceived changes in the lesion may prompt presentation in primary care.
• A convincing history, paediatric notes or photographs may be used to confirm the congenital (or shortly thereafter) nature of the lesion.
• Enquire about and document any recent history of:
  • New bumpiness or nodularity
  • Surrounding redness or oedema
  • Pain in the lesion
  • Tenderness in the lesion
  • Recent itching
  • Recent bleeding
  • Recent oozing, crusting or scaling.
• The lesion should be examined carefully in good light and particular attention paid to:
  • Asymmetry of the lesion?
  • Border – regular or irregular?
  • Colour of the lesion – is it unevenly distributed with different shades of tan, brown and black; has it spread into surrounding skin?
  • Diameter of the lesion and any history of recent change in its size.

• Malignant melanoma
• Halo naevus
• Epidermal naevus syndrome
• Neurofibromata/café-au-lait spots
• Other melanocytic naevi
• Sebaceous naevus
• Spitz naevus
• Pyogenic granuloma
• Basal cell carcinoma
• Histiocytoma
• Nevi of Ota and Ito.

• Typical small/medium lesions with no suspicious features usually require no investigation.
• Dermoscopy may be useful in assessing lesions and determining the degree of suspicion of malignant melanoma.³
• Biopsy of the lesion may be used for suspicious lesions; smaller lesions can be subjected to excision biopsy, larger lesions requiring partial biopsy, possibly with dermatological/plastic surgical advice.
• Congenital pigmented naevi (particularly giant or multiple lesions) can be associated with neurocutaneous melanosis; where this condition is suspected then neuroimaging is advisable, seeking evidence of leptomeningeal melanotic lesions.⁴

Neurocutaneous melanosis.⁴

• If there is a classical history, no features to suggest melanoma and no desire for improved cosmesis by the patient, then reassurance about the nature of the lesion is all that is needed.
• Some advocate regular follow-up of congenital pigmented naevi with recurrent photography ± dermoscopy to screen for changes indicating possible transformation to melanoma.³
• The risk of malignant transformation in small and moderate-sized lesions is probably so small as to justify reassurance alone.
• Larger lesions should perhaps be monitored in a dermatology clinic.
• Those lesions that are most likely to undergo malignant change (giant or multiple) are often those least suited to prophylactic excision; seek dermatological/plastic surgical advice for such lesions.
• Giant congenital lesions may be treated in infancy by recurrent shaving of superficial layers/curettage (melanocytes often typically in superficial layers early on); this appears to decrease the risk of subsequent malignancy but the lesions may become repigmented.⁵

• Malignant transformation to melanoma
• Neurocutaneous melanosis (may cause a variety of neurological problems – particularly hydrocephalus)
• Complications associated with excision of lesions (particularly a problem with very large ones).

• Small or medium congenital melanocytic naevi carry a good prognosis with a low risk of transformation to melanoma.
• Despite the increased risk of melanoma in larger congenital pigmented naevi, the vast majority will not go on to develop melanoma.

To prevent melanoma in all people, but particularly those with large congenital pigmented naevi, advise:

• Reducing UV-light exposure
• Reducing peak sunlight exposure during most intense sun periods
• Use of sunscreens (controversial – some suspect may increase UV-exposure)
• Use of hats and clothing to shield from intense sunlight.