Moles can appear anywhere on the skin, alone or in groups. Their colors can range from light brown to red, blue, dark brown, gray and even black. They may be flat, slightly raised, smooth or rough and may contain dark hairs. Most moles are referred to as benign nevi and, with no changes to them, are harmless. The term dysplastic nevus refers to moles that contain abnormal or atypical cells, which means that changes in the mole, under the skin, have begun to occur. These dysplastic nevi have a greater potential for becoming a melanoma skin cancer, so all dysplastic moles should be removed.