"Ugly Duckling" Sign: Early Melanoma Recognition Tool

The Advent of the Ugly Duckling Concept

In 1998, Grob, et al^[7] introduced the ugly duckling concept-the observation that nevi in the same individual tend to resemble one another, and that MM often deviates from this nevus pattern. This clinical realization pointed to the importance of not just evaluating the morphology of the lesion in question, but also comparing it to that of surrounding lesions, looking for an outlier in the background of similar-appearing moles. For example, the outlier lesion can be larger and darker than the surrounding moles (Figure 1 A), or conversely, small and red in the background of multiple large dark moles (Figure 1 B). Finally, if the patient has few or no other moles (Figure 1 C). any changing lesion should be considered a suspicious outlier.

(Enlarge Image)

Figure 1.

Three Examples of an Ugly Duckling

Three different clinical scenarios are shown where outlier lesions (" ugly ducklings ") should prompt suspicion. Squares A, B, and C each represent a body area such as the back. In A, the patient has one dominant mole pattern with slight variation in size. The outlier lesion is clearly darker and larger than all other moles. In B, the patient has two predominant nevus patterns, one with larger nevi and one with small, darker nevi. The outlier lesion is small but lacks pigmentation. In C, the patient shows only one lesion on the back. If this lesion is changing, symptomatic, or deemed atypical, it should be removed.

The clinician utilizing the ugly duckling sign is engaged in a process called differential recognition. Gachon, et als described the three principle mental processes for image recognition: overall pattern recognition, known as gestalt; analytic criteria recognition such as the ABCDEs; and differential recognition—recognizing the differences between objects—i.e., the ugly duckling concept. In their study, Gachon, et al surveyed dermatologists for perception parameters that prompted surgical removal of pig-mented lesions. Differential recognition of the ugly duckling sign was more discriminatory between MM and other nevi than the ABCDE criteria.^[8]

Cite this: The "Ugly Duckling" Sign: An Early Melanoma Recognition Tool For Clinicians and the Public - Medscape - Sep 18, 2007.

Table 1. Clinical Approach to Pigmented lesions Identifying the Outlier as a Screening Method for Melanoma
Level of Diagnosis	Relevant Signs, Acronyms and Algorithms	Comments
Level 1 "Macro"— screening for the outlier lesion	Patient history of a changing or symptomatic lesion Context: patient age-new lesion in older patient is suspicious number of nevi-atypical lesion in patient with few nevi is suspicious Differential recognition of the" ugly duckling" lesion on the background of the" moles that breed true" New or changed lesion detected compared to baseline total-body photography	Main determinants of sensitivity for melanoma detection
Level 2 "Micro" — individual lesion assessment	Analytical criteria (ABCDE acronym; dermoscopic assessment using algorithms) Pattern analysis (clinical and dermoscopic) Short-term mole monitoring for patterns of change	Main determinants of specificity for melanoma detection
Level 3 — Biopsy

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