Common blue nevus, this is a solitary, asymptomatic, blue and blue-gray nodule.
The blue nevus is a slightly elevated, round, regular nevus, usually less than 0.5 cm, and contains large amounts of pigment located in the dermis. The brown pigment absorbs the longer wavelengths of light and scatters blue light (Tyndall effect). The blue nevus appears in childhood and is most common on the extremities and dorsum of the hands. A rare variant, the cellular blue nevus, is larger (usually greater than 1 cm) and nodular and is frequently located on the buttock.