Congenital melanocytic nevi

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What this article covers

• Overview

  Definition: a congenital melanocytic nevus is a benign proliferation of melanocytes present at birth, typically a solitary hyperpigmented lesion with an increased density of hair follicles and coarse hair.

• Epidemiology

  Present from birth: by definition these lesions are identified at birth or recognized in the newborn period, unlike acquired moles that appear later in childhood.

• Risk factors

  Larger projected size: large and giant nevi carry a higher likelihood of associated complications than small or medium lesions.

• Pathophysiology

  Melanocyte proliferation: the nevus reflects a benign clonal proliferation of melanocytes that arises during embryonic development, before birth.

• Clinical features

  Established at birth: the defining feature is a pigmented, often hyperpigmented lesion documented at birth or in the immediate newborn period, which separates it from acquired melanocytic nevi that appear later in life.

• Differential diagnosis

  Congenital dermal melanocytosis (Mongolian spot): flat, poorly circumscribed, nontender, blue-gray patches that do not blanch, typically over the lower back or sacrum, unlike the raised, often hairy…

• Diagnosis

  Diagnose clinically by history and morphology, then grade by projected adult size: the diagnostic basis is a pigmented lesion documented as present at birth, often with coarse hair; lesions are…

• Management

  First, establish observation as the default for stable, smaller lesions: a solitary lesion projected below 20 cm at maturity, without concerning features, is appropriately managed with observation rather than intervention.

• Complications

  Neurocutaneous melanosis: melanocytic proliferation within the central nervous system can accompany large, giant, or multiple-nevus disease, which is why neuroimaging screening is considered in this group.

• Prognosis

  Favorable for small and medium lesions: most small and medium congenital nevi remain stable and are safely followed with observation and periodic examination.

• Prevention

  True primary prevention is not possible because the nevus is present from birth, so the practical prevention target is early detection of change rather than prevention of the nevus itself.