You can use the alphabetic classification system to evaluate melanoma, the most aggressive form of skin cancer. This guide helps you determine whether a skin lesion is malignant. The mnemonic is the first five letters of the English alphabet — A, B, C, D, and E. Here are the warning signs:

  • A = asymmetry: If one side of the lesion differs from the other, the lesion is more likely to be malignant.

  • B = borders: Are the borders of the skin lesion regular or irregular? Are they smooth or spiculated? The more irregular the borders, the greater the likelihood that you’re dealing with a malignancy.

  • C = colors: The melanoma may have more than one color.

  • D = diameter: The larger the lesion, the greater the risk that it’s melanoma. A skin lesion of more than 9–10 mm is more suspicious for melanoma.

  • E = evolution: How is the lesion changing over time, in terms of appearance and size? Melanoma is more likely to change.

If you suspect melanoma, the next step is a skin biopsy.