nevus /nē″vəs/ [L, naevus, birthmark] , a pigmented skin blemish that is usually benign but may become cancerous. Any change in color, size, or texture or any bleeding or itching of a nevus merits investigation. Nevus is a benign tumor composed of nevus cells that are derived from melanocytes. Also called birthmark, mole1. Also spelled naevus. Kinds include junction nevus, compound nevus, congenital nevus, epidermal nevus. See also blue nevus, nevus flammeus.