naevus

Naevus, or nevus, is a benign skin lesion caused by localized proliferation of melanocytic cells derived from the neural crest. Nevi are commonly called moles or birthmarks and may be present at birth or appear during childhood or adolescence. Most nevi are harmless, but some variants carry higher risks or require monitoring.

Nevi are typically classified histologically into junctional, compound, and intradermal types, depending on the location of nevus cells relative to the dermoepidermal junction. Clinically recognized variants include blue nevus, Spitz nevus, and dysplastic (atypical) nevi. Congenital nevi are present at birth; giant congenital nevi carry a higher risk of melanoma and may require ongoing surveillance or removal. Dysplastic nevi have irregular borders and color and may be associated with an increased melanoma risk, particularly when numerous.

Risk factors for nevi include genetic predisposition and sun exposure. Diagnosis is usually clinical, aided by dermoscopy; excisional biopsy is performed if malignancy is suspected. Any change in a nevus’s size, shape, color, or the onset of symptoms such as itching or bleeding warrants evaluation.

Management is typically conservative, with removal reserved for cosmetic reasons or to rule out melanoma. Removal methods include shave, excision, or punch biopsy, with complete excision preferred when malignancy cannot be excluded.

Prognosis is generally excellent for typical nevi. The risk of malignant transformation is low for common acquired nevi but higher for dysplastic or giant congenital nevi. Regular skin self-examination and prompt medical assessment of suspicious lesions are advised.