A benign collection of pigment-producing cells (melanocytes) in the epidermis, dermis, or both.
Can be present at birth or shortly thereafter, or acquired throughout childhood, peaking during the third decade.
Seen in all races. Dysplastic or Clark's nevi are more commonly seen in white people.
Melanoma is the most important differential diagnosis when examining melanocytic nevi. Asymmetry, border irregularity, colour variegation, diameter >6 mm, and evolution or change in a pigmented lesion (ABCDEs) may signify concern for malignancy.
Diagnosis is usually clinical, although dermatoscopy and/or biopsy can be utilised to further examine the lesion in cases where there may be uncertainty as to the diagnosis or a concern for malignancy.
Important reasons for removal of a melanocytic nevus are: high clinical suspicion of melanoma; history of change in the lesion, supported by physical examination; and/or high suspicion of atypical features suggestive of melanoma.
Melanocytic nevi are a group of benign neoplasms or hamartomas made up of melanocytes, the pigment-producing cells of the epidermis. They can present in a variety of ways, most commonly as small, brown, flat macules, raised mammillated dome-shaped papules, bluish-grey macules and papules, and even amelanotic skin-coloured papules. Unless congenital, they first appear in childhood and are more common in people with light skin and eyes. 
Professor of Dermatology & Cutaneous Biology
Director of Dermatopathology Fellowship
Director of Pigmented Lesion Clinic
Thomas Jefferson University
JBL declares that he has no competing interests.
Dr Jason B. Lee would like to gratefully acknowledge Dr Laurel R. Schwartz, a previous contributor to this topic. LRS declares that she has no competing interests.
Department of Medicine
Medical College of Ohio
CGB declares that he has no competing interests.
MH declares that he has no competing interests.
West Herts NHS Trust and King's College London
VB declares that she has no competing interests.
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