Although pigmented nevi are among the most common of these skin growths, other varieties of nevus are also known.
A local increase in the concentration of melanocytes is termed a melanocytic or pigmented nevus; an area of increased capillary concentration, a capillary nevus.
They may be benign (such as a nevus or a mole) or malignant (such as melanoma).
A common genetic abnormality is the nevus, often called a mole or birthmark.
Epidermal nevi, of which the sebaceous nevus is an example, develop from the proliferation of normal epidermal tissues and are usually flesh-coloured or yellowish.
In nevus anemicus, an area of skin is pale because of reduced blood flow, even though there is no evidence of a structural disorder.
In other types, such as the blue nevus, proliferative tissue is buried deep within the dermis, the lower layer of the skin.
Premalignant nevi include the sebaceous nevus, a congenital formation containing hair follicles and sebaceous glands, and the giant pigmented, or bathing trunk, nevus, a large, irregular, dark brown or black patch associated with malignant melanoma.
Some pigmented nevi, such as the blue nevus and the junctional nevus, may be associated with skin cancers but are not widely considered precancerous.
The skin should always be inspected for cancer, though it is sometimes difficult to differentiate a benign mole (nevus) from a cancer.
Change in shape, size, or colour of a nevus may indicate transformation into a malignant tumour.
