Common acquired nevi, or moles, are composed of nevus cells (melanocytes) grouped in collections within the first and/or second layers of the skin. They have a wide range of presentation and can occur on any surface of the skin or mucous membranes, including the nail beds.
There is a higher prevalence of nevi in people with light skin compared to those with dark skin. Common acquired nevi usually first appear between the ages of 6 to 12 months. They become more numerous in childhood and the teenage years, and tend to regress later in life.
Cause of Common Moles
The tendency to develop nevi is influenced by familial factors and sun exposure.
Signs and Symptoms of Common Moles
Common acquired nevi vary in size, color, and shape. They are typically 3 to 5 millimeters in diameter and may be light or dark in color, and flat, raised, or polypoid in shape. Hair may be present on the mole. A pigmented nevus in the nail bed appears as a light to dark brown streak extending from the cuticle to the end of the nail. In some cases, the cuticle skin and the tip of the finger or toe can be pigmented as well.
Typically, common nevi have very clear lines of demarcation and their borders are obvious. Hair, when present, is usually dark and coarse. Typical acquired nevi have a minimal risk of becoming cancerous.