Moles, or naevi, are brown or tan spots on the skin that result in the clustering of melanocytes (pigment cells of the skin).

Melanocytes (cells that produce pigment) are present in the lowest layer of the epidermis- the outer barrier of the skin. With certain forms of stimulation; such as the ultraviolet irradiation (i.e. usually from sunlight), the density of melanocytes in normal skin may increase.

Melanocytic naevi represent normal, harmless proliferations of melanocytes that are in contact with each other, forming small collections of cells known as nests. They are common lesions found on the skin of almost all individuals. Some patients have a few naevi, while others have hundreds.

Most melanocytic naevi are benign (i.e. non-cancerous). However up to 40% of melanomas are associated with a pre-existing melanocytic naevus, meaning up to 60% of melanomas arise in normal appearing skin. The main thing to look out for is change in size, colour or shape of a melanocytic naevus as this will be the earliest sign that a melanoma could be developing. Dysplastic naevi are variants melanocytic naevi. They often appear as target-like or fried egg–like skin lesions. It is controversial as to whether a patient with these has an increased risk of melanoma. Treatment for melanocytic naevi will vary on an individual basis. Many can be left, as they are usually benign, some may be monitored or surgically excised depending on your doctor’s advice.

Examples of Melanocytic Naevus