The ABCDEF Rule: Combining the “ABCDE Rule” and the “Ugly Duckling Sign” in an Effort to Improve Patient Self-Screening Examinations

To the editor:

Regular self-skin examinations by patients have been shown to decrease the depth of melanomas at the time of diagnosis and facilitate a lower risk of melanoma when coupled with regular visits with a physician.1 Accordingly, the American Academy of Dermatology has sought to improve patient awareness of melanoma through its SPOT Skin Cancer campaign.2 At our institution, we counsel patients to perform regular self-skin examinations in an effort to expedite identification and appropriate treatment of suspicious melanocytic lesions. To aid patients in identifying possible melanoma, we often recommend the use of either the “ABCDE rule” or the “ugly duckling sign.”

The ABCDE rule, first introduced in 1985 as the ABCD rule3 and then expanded in 2004 to the ABCDE rule,4 encompasses several clinical features of melanoma, including Asymmetry, Border irregularity, Color variation (both intralesional color variation as well as a color that is different from the patient’s other nevi), Diameter greater than 6mm, and Evolving (a new or changing lesion). An alternative to the ABCDE rule, the “ugly duckling sign,” was later developed to address the limitations of the ABCDE rule.5 It states that the “spot” that is unlike the others is often the most suspect for malignancy. Their limitations aside, both of these methods provide an easy, general framework from which patients may work in order to identify potential melanomas.

Due to time constraints or personal preference, dermatologists often choose to counsel patients on one of these guidelines while neglecting the other. However, the shortcoming of using only one of these criteria is that the ABCDE and “ugly duckling” rules are complementary to one another and are not necessarily equal alternatives to one another. That is, the ABCDE rule does not account for the added screening benefits of using the “ugly duckling rule,” and vice versa.

Therefore, we propose a modification to the ABCDE rule in order to combine the benefits of this rule with that of the “ugly duckling sign.” The addition of the letter “F,” which stands for “Funny looking,” nicely incorporates the “ugly duckling rule” into one, unified tool—the ABCDEF rule—for patients to use when evaluating their moles at home. The “Funny looking” mole, like the “ugly duckling sign,” implies that there is an overall gestalt one can have about a spot being suspicious.

The addition of another letter to the currently widely used ABCDE rule does not seem to overly complicate the mnemonic for patients. Indeed, in our experience in counseling patients about the ABCDEF rule, we have found that the inclusion of a somewhat humorous and unexpected “capstone” to the mnemonic has been very well received. The ABCDEF rule improves upon the previous iteration of the mnemonic and may prove to be a useful tool for patients and physicians alike in identifying worrisome melanocytic lesions.