Dysplastic nevi are moles that are larger than average (larger than a pencil eraser) and irregular in shape. They tend to have uneven color with dark brown centers and lighter, uneven edges. These moles tend to be hereditary (passed on from parent to child through genes). People with dysplastic nevi may have more than 100 moles and have a greater chance of developing melanoma, a serious form of skin cancer. Any changes in a mole should be checked by a dermatologist to detect skin cancer. Read more about moles, freckles and skin tags.