Warning Signs of Cancerous Moles (ABCDE Rule) Asymmetry: Benign moles are mostly symmetrical; irregular shape is suspicious. Border: Blurred, jagged, or uneven edges. Color: Uneven mixing of black, brown, blue, white, or other colors. Diameter: Larger than 6mm, or growing rapidly in a short time. Evolution: Changing quickly—itching, ulceration, oozing, crusting, or swelling.