Asymmetrical

• Benign (non-cancerous and non-malignant) moles are typically round.
• Asymmetrical: Melanoma (cancerous and malignant) lesions are typically irregular in shape. (Asymmetrical)

Border

• even: Benign moles have smooth, even borders.
• ragged or notched edges: Melanoma lesions often have uneven borders.

Color

• single shade: Benign moles are usually a single shade of brown.
• many shades: Melanoma lesions often contain many shades of brown or black.

Diameter

• <6mm or 1/4”: Benign moles are usually less than 6 millimeters in diameter.
• >6mm or 1/4”: Melanoma lesions are often more than 6 millimeters in diameter.

Evolving

• flat: Benign moles usually do not change size over time.
• elevated: Melanoma lesions often grow in size or change in height rapidly.
  

Source: NCI Visuals Online. Skin Cancer Foundation.
http://visualsonline.cancer.gov/about.cfm